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.

[Second Series]

I was concerned with ride height, so I measured from the top of the frame to the bottom of the springs. The ’47 is 10", the ’88 is 13". If I place the ’47 body on the ’88 frame, the relative position of the wheel to the wheel well will be 3" greater than the stock ’47.

[Second Series]

The ’47 has 2" wood mounting blocks. There are rails across the bed underside. The bed can be mounted closer to the frame by removing the wood blocks and modifying the rails. It looks like I can set the ’47 body on the ’88 frame and maintain the stock ’47 stance.

[Second Series]

I have LT245/75R16 tires on the rear currently. Those are about 30" tall. If I maintain this stance, the space between the top of the rear tire and the fender will be 4". The fender opening is 31" so I won’t run a taller tire without modification.

[Second Series]

This rear end is from an ’86 suburban. I chose rims for clearance of the tie rod ends, so 3.5" back spacing. There is some room to move the wheels in with greater back spacing. I’ll get exact measurements for that. I plan on keeping the 8 lug rear axle, and modifying the front of the donor rig to 8 lug.

[Second Series]

The rear tires are 74" wide and the front tires are 63" wide on the ’47.

[Second Series]

The ’88 tires are 71". This will move the tires out 3.5" on the ’47. With an adjustment to the wheel back spacing, the tires should fit inside the fender.

[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.

[Second Series]

From the manual:

[Second Series]

There is also a switch in the lock cylinder that triggers the buzzer if the door opens with the key still in. I won’t have that.


Here is a diagram of the ’88 ignition switch.

[Second Series]

I’ll create a spreadsheet, a truth table of how the switch works based on this diagram and the schematics.
This shows the connector and pins 2, 3, 6/5.

[Second Series]

This includes pin 4.

[Second Series]

And this identifies pin 33.

[Second Series]

How does this relate to my truck? Heres the connector: