1947 Panel Truck Frame swap with ’88 k2500

[Second Series]

This is my 1947 chevy panel truck. I plan on making it a reliable daily driver.
After a couple years of searching I found this 1 ton panel truck. It was listed in the greensheet for $800.
I responded to the ad and the seller told me it was in a storage yard. I rushed down there to have a look, the yard was locked, so I went through some woods to the side and saw the truck. I knew it was right when I saw it. In my excitement and haste I tripped and fell on some mesquite, jabbed a thorn into my palm.
I arrange a time to meet and showed up with a AAA towtruck and my weeks pay in my pocket, $200. Mike was sad to let it go, but he saw my enthusiasm. He had big plans and also had a 350 torn apart. He wanted to go through everything and build it right. He hadn’t done much in the 10 years he owned it. Some boyscouts had recently broken the windows, so he decided to it was time to sell. I handed him the $200 and said I would pay the rest each week with every dollar I earned. He just said to go ahead and don’t worry about it. I had it towed to the driveway of the house I was renting where I replaced the windshield and door windows. Later I had it towed to a storage space where I rebuilt the brake cylinders.
After two years, I went to a junk yard and asked if they had an engine for me. Recently a ’58 DelRey with a pickup camper mounted to the back half had arrived. This was a dream machine that a mechanic had built to live in during his battle with cancer. I purchased the 235 and had them remove it and deliver it to a mechanic. At the time I was living in a ’58 Viking bus RV in a trailer park. There was a mechanic next door that agreed to take on my project. They set up the engine and told me to get “the Beast” out of their yard. I stored it for another year at the neighbors. I found another mechanic to continue. I went back to the junkyard and found a dumptruck with an SM420 transmission. I had to go back several times to wrestle that out. The mechanic was making slow progress. I had gotten my truck stuck in the mud, so I went to the mechanic and told them my panel truck was ready. I started driving it to work until I got my truck unstuck.
I had to get it legal, so I had a patrolman come out and verify the numbers. They took the number off the engine, I wasn’t there at the time but my neighbor in the trailer park said he had trouble finding the number. Titled and insured I worked on it now and then and drove it occasionally. Off to college I would drive between Waco and Austin for the weekends. My F100 threw a rod, so I started making the 2 hour trip in the panel truck. I could go 60 mph floored. It was loud, shakey, and walked a couple feet when hitting a bump. There was an old F250 with 3.55 gears behind my girlfriends place in the woods. I had the panel truck jacked up on stumps in the mud swapping that in. Pulled some U-bolts from a junk yard and made an offset by drilling a couple holes in metal plate. I didn’t like it. Yes it was faster, but behind the 235/SM420, I had to start in the compound low every time unless going downhill. If I rolled up to a light that just changed from red to green, the engine would struggle in 2nd gear, or I would have to stop and shift to 1st. I had float shifted in the f100 on the highway, so I knew it could be done. Might be o.k. on a country road, but I needed consistent drivability in the busy city. That and one axle was bent.
I found a rear end from an 86 suburban with 3.73 gears. Now I could go 80 mph floored, loud shakey and walking a foot or two when hitting a bump. It would also make a sound at higher speeds, maybe the angles of the driveshaft. I would tell passengers it’s balking. Mostly a weekender, driving around town or short trips vehicle. One day there was a wretched sound from the engine compartment, a loud rattle. I pulled to the side of the road and shut it off. When I started it again, the valve that had snapped, wedged between the head and cylinder, engine siezed. I had another 235 installed.
I trailered it to Seattle and was commuting across town for a few years. I had the knee action shocks replaced with cylider shocks, and also added shocks on the rear as well as get the rear end re-installed correctly. The shocks helped eliminate the walking sideways when hitting a bump at high speed. I decided to get the numbers on the title squared away since the vin was from the blown engine I left in Texas. Washington had issued me a title when I surrendered the Texas title. I got the appropriate documents and drove to the state patrol where they looked at the ID plate and agreed to issue a title based on the number on the ID plate.
I really had to stand on the brake pedal when stopped on a hill, no fun. It mostly just sits. I start it every month and drive around a little. I want this to be my main vehicle. I could drive it around running errands, but after it gets hot, it is difficult to start. I have to not touch the gas pedal, and maybe it will start, or I’ll have to wait awhile. I need to be able to get in and go! A few years ago I picked up a 1988 GMC k2500 to use as a donor. Recently I found a shop to take on this project. I have been looking at options and haven’t found anything close to home. I went by one custom shop and they said there is a two year backlog. They also said they don’t know how to NOT take everything apart, blast everything, paint everything, and put it all back together. I just happened to stumble across a compound with several shops and walked into the body shop. At first they thought I was crazy and said they do $10,000 paint jobs, but as we talked, he said they don’t usually do that kind of work, but it would be fun. It’s a shop with a floor and tools and resources, I have none of that so this may be the place.
TLDR: Frame swap ’47 panel truck with ’88 k2500. I’ve had the panel truck for over 20 years and daily driver for 10.

[Second Series]

I’ll farm out the heavy lifting and work on what I can. Before I get too far will it work? Here is what I have mocked up.

[mongocanfly]

thats gonna be a ambitious project...as you can tell from your drawing ,the panel will have to sit really high above the frame...unless you cut the floor out...also the width will be a issue....k20 is considerably wider than a AD..

[MiraclePieCo]

Cool background story, cool truck. You're not the guy who bought my 1-ton panel rear bumper and brackets, are you?

Your chassis swap sounds like one of those projects that will never be finished. Better idea: completely rebuild the original front and rear suspension, disc brakes up front, all new drums in the rear. New carburetor and ignition system. Overdrive transmission to run at modern freeway speeds. Electric wipers, interior sound deadening, new window channels and weatherstrip all around. It will be like a new vehicle.

[Second Series]

“thats gonna be a ambitious project...” - Mongo...aka Greg
Agreed. Since I have both trucks, I took a tape measure to them.

“Cool background story, cool truck. You're not the guy who bought my 1-ton panel rear bumper and brackets, are you? “ -MiraclePieCo
Thanks! This truck was near complete when I got it, minus engine and transmission. I did install an electric wiper, but it is just as slow as the vacuum was. I am able to use the later wiper arms with springs to hold the blades on the glass, but it’s not fast enough for a torrentioal downpour.

The wheelbase is the first thing I considered when determining a donor frame. The 1947.2 wheelbase is 137". The 1988 K2500 single cab long bed wheelbase is 131.5".
The frame width is going to have to work. ’47 1 ton is about 35", the ’88 K2500 is 45". There needs to be 5" of clearance outside of the ’47 frame for this to work.

[Second Series]

There is about 10" between the frame and running board.

[Second Series]

The ’88 frame drops 8" under the cab. The ’47 battery tray will need to be trimmed. I’ll replace the battery tray with a box for storage or electronics.

[mongocanfly]

Looks like your doing your homework...

[Dan Bowles]

I know you already have the one but an X cab frame is slightly longer. About 141.5" or so. I started this with my son's truck once upon a time but he decided to stay straight axle. There is a seam under the 88's doors that takes the front cradle from boxed to the rear C channel. You can grind the welds out and cut the frame to length in 10 minutes. It is the same as doing an S10 swap using an X cab S10 frame. The 1 ton wheelbase is actually about 1.5" shorter than it should be so adding that back in you'd be about 140" for a rear centering wheel base.

There are several guys that have done this swap with pickups and they don't come out too bad. Late model HD rims look pretty sweet on these trucks, especially if powdercoated in a gray/silver color rather than the polished finish. 2008+ centercaps on them don't look so bad with them. I'll get you some photos from his truck as it sits.

If you are really concerned about width, you can swap a 1.5+ ton nose on and look at widening rear fenders. The one thing I would caution is make sure the damn rear wheels will come off with the fenders on. We have a set of rims with a deeper offset but couldn't get them onto the stock axle with spacers. We will swap to an 88+ 3.73 rear end here this summer but had to go back to the HDs because we just couldn't fit them onto the rear without dropping an axle because the fender hits!

Good luck. I'll keep an eye on this one. I've had 2 of those 3800s run through here and I dig them. 2 3800 pickups as well. I walked past Eli's 49 panel last night and thought "my suburban looks like a baby".

[Second Series]

Thanks for the feedback. I'm not too concerned with the wheels sticking out of the wheel wells, just addressing the issue beforehand. I'm kind of dragging my feet at this point, waiting until fall to start. I'm going through the different systems, planning how each will work. I'll use the stock gauges, so a bit of design work there. I figured out how to keep the stock ignition switch and foot starter. I'll look at everything else on the wiring diagram, I'd like to eliminate the bulkhead connector if I can. I'll look into building a drive for the speedometer too.

[Dan Bowles]

Originally Posted by Second Series

Thanks for the feedback. I'm not too concerned with the wheels sticking out of the wheel wells, just addressing the issue beforehand. I'm kind of dragging my feet at this point, waiting until fall to start. I'm going through the different systems, planning how each will work. I'll use the stock gauges, so a bit of design work there. I figured out how to keep the stock ignition switch and foot starter. I'll look at everything else on the wiring diagram, I'd like to eliminate the bulkhead connector if I can. I'll look into building a drive for the speedometer too.

I think it's Bob's Speedometer in Michigan that can do the electric to mechanical speedo conversion. I've talked to them a bit but not gone any further than that. It's around $250 IIRC but something I don't know if I could make on my own without some study!

[Second Series]

I just looked on Bob’s website, they show the Cable-X, Cable-X site lists it at $340. Dakota Digital is $285, Speedhut is $360. There may be others, this is just from a quick search this morning. I’ll look into reviews of what’s available.
I read a post about converting a ’89 Blazer transfer case mechanical to ’90-’91 electrical speedo, so it may be possible to go the other way. I also read that Dodge used a mechanical speedo on the NV4500 at some point. I have a 5LM60 now, and I understand that is identical to the NV3500 on the outside. If I can get it set up with a mechanical speedo drive, I’ll go that route. I’ll still need the electronic signal. If I have to remove the tone ring, I may be able to get an in-line VSS. Stealth Conversions made one for the 4-pulse system, there are bound to be others. This is partly speculation, I’ll take my time and create a detailed document.
Dan, how about a pic of your son’s truck?
My k2500 is the 6-lug. Does the 8-lug k2500 have a wider tread? I read where someone swapped the 6-lug to 8-lug spindle and modified the upper A-arm, that’s my plan. The diffs are 3.73, the ’88 8-lug rear in the ’47 is also 3.73. I was concerned about how the rear works with the RWAL (Rear Wheel Anti-Lock) system. I don’t see any wires to the rear axle. The schematic show the VSS supplies the signal for that system, so it should be good to swap the rear.

[Second Series]

I intend to keep the original key switch in the ’47, and modify the foot button to work with the ’88 system. My list of objectives:
1. Retain the original ignition key switch and foot starter.
2. Adapt donor circuit to function from original key and footbutton
3. Modify foot button bracket to actuate momentary switch, relocate switch-originally on starter.
Is there room between the lower firewall and the rear of the engine?
First I’ll identify how the donor key switch functions.

From the manual:
STEERING COLUMN HARNESS CONNECTIONS
The steering column harness branches from the instrument panel harness and then to the turn signal or multifunction lever switch connector, the windshield wiper connector, ignition switch connector, the brake pedal ' 5 switch, connector, the dimmer switch connector, the , back-up switch connector, the position sensor connector ’ and the horn switch. Refer to figure 24 and to ACCESSORIES (SEC. 9) for the multi-function lever switch.

This image shows the Ignition switch connector, 232.

[Dan Bowles]

Originally Posted by Second Series

My k2500 is the 6-lug. Does the 8-lug k2500 have a wider tread? I read where someone swapped the 6-lug to 8-lug spindle and modified the upper A-arm, that’s my plan. The diffs are 3.73, the ’88 8-lug rear in the ’47 is also 3.73. I was concerned about how the rear works with the RWAL (Rear Wheel Anti-Lock) system. I don’t see any wires to the rear axle. The schematic show the VSS supplies the signal for that system, so it should be good to swap the rear.

My local guy swapped his completely over to 8 lug with little or no effort. Swapped spindles and the axle. I don't think there is a significant width difference. Anti-lock I think just was a speed sensor in trans for 88. Nothing high tech there and you can by-pass it by ripping out the ABS box and running brakes direct. Those things are probably failed by now anyway!

I'll get pics of Eli's truck soon. He's tearing stuff apart again working on some body work right now. It's been up and down over the last 10 years. A giant wheelbarrow full of storage for at least 6. The nice thing was getting a set of 93-94 extended cab bucket seats. They sit almost perfect on the riser and give you a flip forward/slide forward option on the passenger seat for rear access if you need. No major mounting issues, either because the frames are about square and flat unlike about every other front seat you run into!

[MiraclePieCo]

This is an exciting build. I really dig those 1-ton panels. I'll be watching!

[Second Series]

Each week I visit the shop, a little progress has been made. Last week the body was on a cart, and the two frames were side by side. Comparing body mounting points and deciding how to modify the donor frame. The ’47 gas filler is on the passenger side. 1988 the filler is on the driver side, tank is inside the frame rail. Pre ’88 the tanks were outside the frame and an auxilliary tank could be added to the passenger side. That doesn’t appear to be an option here, the ’88 auxiliary tank was behind the axle and I want the spare tire there. It could be done, re-route the exhaust to the driver side and find a tank with the passenger side filler. There is the driver side transfer case, so exhaust would go below that. I may go with moving the filler to the driver side on the panel. Here is a picture from a couple weeks ago…

[Second Series]

Little progress has been made since last week, but a little progress each week will get the job done. Fuel tank removed and exhaust cut. I have been researching how to use the stock instrument cluster and speedometer. I took the instrument cluster to hook it up to my ’90 chevy so I’ll have that working when this project is ready. I may be able to replace the 40 tooth reluctor in the transfer case tailhousing with a mechanical speedometer drive, and use a mechanical to electric pass through adapter for the DRAC. I’ll either build my own DRAC, or get one from a ’91-’94 truck. The ’88 DRAC is integrated in the display pcb…

[Purcell69]

I really like what you've got going. Like others have already mentioned, due to the newer frame configuration, you will either need to raise the body mounts or raise the floor of the truck to recess the frame in to it. Personally, I would build the body mounts up to work with the stock cab floor. That is what I did. I can't stand a truck with a bed that is only 6" deep. I use my bed and don't like the look of the "non-functional" bed, but that is just personal preference.

The other issue will be track width. Your tires will stick out past the fenders to some extent. Some of this can be minimized with wheel offset, but unless you go to lengths to widen the body or flare the fenders, the tires will stick out. With tall/skinnys on stock offset wheels, mine stick out about 1.5" per side. Again, this is personal preference.

Getting the wheelbase to fit the body is the biggest part of the battle and it looks like you have a good start on that. You may need to extend the front and rear of the frame for your body mounts, but that can be done with some 10 gauge steel.

Since you have the original frame, you can replicate the profile of the frame rails using square tube laid across the new frame and then build your body mounts from there. Again, this was how I chose to do it.

I think this will be a great daily driver when you are done. Unique, reliable and easy to work on and enjoy. None of that is wrong. I'm looking forward to see where this goes.

The red truck is a local. I don't know what specific chassis he used but it is 1973-1987 GM 4x4 K10.

-Joe

[Second Series]

Thanks Joe, I feel the same about the functionality of the bed. The panel truck bed will be as close to the frame as possible. The cab floor is lower than the bed and the donor frame is lower under the cab, so it should work good. It looks like the cab floor will be near the level of the top of the transmission, so no hump needed. I dig that red truck, I don’t think mine will be that high, one of the reasons I will not use a solid front axle. Not much progress this week, but the plan is to remove the rear end and build a body mount template out of 1” L-stock. You may notice in the picture in my previous post, the frame appears to be higher in the rear driver side, we’ll check that at the alignment shop. We’ll use the brackets and frame ends from the ’47 frame. The original frame had extensions on the rear.

[Rusti]

Very interesting way to work with a second frame.
So Long
Arnd

[Second Series]

The body is on the donor frame, it has a 2x4 under the front in the picture, still needs some adjustments. The bottom of the firewall above the transmission will be modified. The rear of the rear inner wheel well will be trimmed to accommodate the leaf spring. The 1x2 cross sills have the bed as low as it can go without major mods.
The next step is to hang the fenders, start carving the front inner fenders, and locate the running board brackets. The front and rear running board brackets have conflicts, so will need to be moved. The radiator will need to negotiate it’s placement based on the location of the steering gear. I got a desert cooler radiator 25+ years ago, it should be good for this 350. I’m just not sure about the horizontal vs. vertical flow.
I’m still working on the motor drive for the mechanical speedometer. I found a motor with the right range, now I’m working on the code to convert frequency to PWM. I also need a DRAC module since my DRAC is incorporated into the gauge cluster pcb. I went to a scrapyard yesterday, but all the trucks had the electronics removed.
It was a good feeling to see the body on the frame, this is a good milestone in the build. There is still a long way to go, but this is a positive turn.

[Second Series]

Originally Posted by Rusti

Very interesting way to work with a second frame.
So Long
Arnd

I have know the frame can be cut and lengthened or shortened. This kind of frame has a C-channel back into a boxed front. That joint can be cut and the length modified. I thought the rear axle could simply be moved back, so that's how we went, and then add extensions to the front and back to lengthen the frame.
I had read about someone using plywood for the body mounts locations when doing a frame swap, another suggestion was metal. We had some issues with the metal template, interfering with the donor front suspension, modified that. Then the running board part was too narrow so we had to raise up the template. It got the job done.

[Second Series]

Back on this. The rear fenders are set in place, and the runningboard brackets placement are being located. You can see where the Mr. Peanut was removed from the side, and the 5¢ on the door. The rear tire is inside the fender, I’m curious how the front tire will be. The rear wheel might could be moved ½” forward to center in the wheelwell. I didn’t measure, but it looks like the distance from the top of the tire to the wheelwell is close to the 4” = stock height. In my preliminary plans I figured the stock height could be preserved if we removed the 2” wood blocks, and replaced the 2+” hat channel cross sills with 1x2 tube. After teardown and using the body/frame template, we thought it would have a 2” lift. Now that it’s coming together, things are lining up well. There is plenty of clearance between firewall and engine. The firewall had to be modified just above the transmission, but not much. Next steps are to attach the runningboard brackets, modify the front inner fenders. Once the front fenders are in place, the core support will be addressed.

[Second Series]

I like how the front tires don’t stick out of the fenders, they are just inside. I may be able to run wheels with a greater positive offset to suck the tires in. The fan and fan clutch are being greedy in the core support area. We’ll get the grill and support panel mocked up and see how a radiator will fit.

[Purcell69]

Originally Posted by Second Series

I like how the front tires don’t stick out of the fenders, they are just inside. I may be able to run wheels with a greater positive offset to suck the tires in. The fan and fan clutch are being greedy in the core support area. We’ll get the grill and support panel mocked up and see how a radiator will fit.

Have you considered running a two speed electric fan? When I put Ethyl on the 1994 Dodge chassis, I was concerned about space up front, so I moved the engine and transmission 3" back, which was about as far back as I could go with the 1957 firewall. This of course snowballed things a bit, in that I needed to have a new front driveshaft built to add in extra length. I still went with two speed electric fan from a 1995 Ford Taurus V6, the same one the rock crawling guys use in their Jeeps. Those things move an honest 4000 cfm in high speed mode. In the end, I have more room up front which made building a lower radiator hose easier.

I'm impressed with the build. You've really done your homework as far as getting things to fit. It really is a good feeling seeing the body on the frame for the first time. I used 3/16" plate steel to make my body mounts, for what it is worth.

-Joe