Newbie's first post: Advice and ideas please?

[GloryDaze]

I've got a 1967 GMC C20 4x4 I'm looking to restore. Body is really solid, only needs rockers, floor pans and minor dent repair.

It has the 305e big block V6, Muncie sm420 4 speed, and 4.56 gears. The motor runs surprisingly smooth, but not sure it's what I want. I plan to put a small lift on the truck, 3-4 inches, followed with 33s or 35s - and I think that should actually help this truck move along with those big gears and 4 speed. Right now it runs out of gear immediately and tops out at 60 miles per hour. I'm not trying to break any speed records, but I would like to be able to take the truck to neighboring cities for car shows, etc.


My friend says I should just find a donor truck and switch everything over to a sbc so I can enjoy it. My classic car mentor says that if the drive train has worked for 45 years I'd be a damn fool to mess with it now.

Also, I can't seem to find a power steering set up anywhere. I spent hours going through the junkyards the other day because I needed a tilt column and wanted power steering. Found the column, but of about 60 67-72 trucks, did not find a single one that looked anything like mine. My front end actually more closely resembles one that I found in an old Dodge. So I'm guessing the previous owner, who used the truck in truckpulls, has swapped the front end to something different.


Anyhow, I'm just curious what some of you guys with more experience have done or would do.

[custom1970]

Any way you could post some pics of that front end??

[SeeTen]

Sounds like a good find! 4X4 is always nice, an once that 305 V6 is outta there, you won't need to break the bank to cruise it around!

I'm curious now too... I'll be waiting for those pics of the front end!

[SS Tim]

It does not look like most trucks because it is likely the stock closed knucle front axle. These trucks like your 3/4 was a work truck. The V6 is a very heavy, medium duty truck engine not a freeway speed cruiser. Have you looked at the carb. It is a grunt engine and single digit gas mileage is almost a norm for this setup.
If you "swap everything over" you just built a truck. If you want a more modern truck with open axles, P/S, automatic and parts friendly transfer case you need to make a decision. The best would be to build one up from a later truck like a 71-72 and either keep this as a stock driver until its done or sell it to someone who wants one of these fairly rare trucks.
The power steering system used is an external ram set up that I have posted some pictures of below. One of the trucks also has a plow frame but you get the idea of what a collection of rare parts it is. Not trying to be a kill joy here but far too often these HD trucks get modified and "improved" to the point that the original builder becomes uninterested in a never ending project and sells it. Then typically a chain of buyers until it is cheap enough and missing enought parts that it becomes parts.

[GMCJOE]

I agree with Tim. Also, unless someone swapped the gear's out, I would have to say you probably don't have 4.56 gear ratio. Far as I know from factory, the only options were: 3.08, 3.42, 3.73, and 4.11 I am by know means a expert on this, so I could be wrong. It would be interesting to know if there was more gear options from factory.

[GMCJOE]

Originally Posted by GMCJOE

I agree with Tim. Also, unless someone swapped the gear's out, I would have to say you probably don't have 4.56 gear ratio. Far as I know from factory, the only options were: 3.08, 3.42, 3.73, and 4.11 I am by know means a expert on this, so I could be wrong. It would be interesting to know if there was more gear options from factory.

And research has proved to me more options. LMC showed me a few more gear ratio's. Learned something new today.

[truckster]

The 305 V6 is an almost indestructible engine. I had one in a 66 GMC 1/2 ton and it would outpull my father-in-law's Ford 390.

[SS Tim]

4.57 gears were the base I6 ratio and 4.11s on the V8s on K20s through '72

[GloryDaze]

Here's a few pics. I'd love any ideas on the power steering, it looks similar to the Ram setup pictured earlier. At this point, I love everything about the truck other than the horrid paint job and Big Block v6. I know it's super reliable and I know it would pull a house - but I plan to drive the truck often and on the highway.

For now, I've put 50 pounds of air in the front tires and that helps the big lug turn. I'm just a set of points and a new front brake away from running a few tanks of gas through this beast.

Unfortunately, there's no simple swapping to a sbc on this one.
I've been told that I could keep the same tranny, transfer, etc. - if I could find the right bellhousing for a sbc. But I have my doubts ... Beginning to think my buddy was right (he insists a donor truck/total swap is the best option.)

So any tips on motor swapping or power steering are greatly appreciated.

[GMCJOE]

The bell housing on your transmission should bolt up to a SBC with no issues, but there is conflicting research on many other websites. You may just need an adapter, some research says most of these trucks with this engine came with a SAE adapter from factory for engine swapping. Not sure on any of the previous, just a bunch of gathered research I have done. In my opinion, this truck is pretty neat with that engine in it and would keep it that way. I have probably only seen a couple other trucks in my time with the 305 v-6's still in them. Though, I have probably walked by several in the junk yard's and not payed any mind to them.

You decide to swap the motor out to a v-8, keep me in mind if you want to sell this one. I live in Kansas and will make the drive out there to get it for the right price.

For you highway speed's, I would suggest swapping your gear ratio's out to 3.73's. Not sure how the power would feel with the current 305 v-6 in it. I would suggest the same even with a v-8 sitting under the hood, you will still turn some pretty high RPM's with 4.56's and top out.

Power steering, I can't suggest much there. Haven't messed around with a GMC/Chevy truck with that setup. Though, I have no doubt's someone has put on a power steering gear box to run with that setup.

[GloryDaze]

I figure the 4.56 might be about right if I swap out the springs to a bit of a lift and run 35s.

Making my decision a little harder, is the fact that the kid I bought it from didn't know ANYTHING about the guy who had it before. That's the guy who supposedly took it to truck pulls. He claims the rear end is completely rebuilt, the front end isn't stock, and again "supposedly" he had put thousands in the motor. I figured that was all BS, but things look and run awfully good.

What's a good running 305 big block v6 worth?

[GMCJOE]

I haven't got a clue on what it is worth.

Not much research info on the worth of them, just like the bolt pattern for the bell housing. Some say the SBC bolts up to the manual trans, others say needs adapter plate, and some even say an automatic transmission will bolt right up to the 305 big block v-6. I think you need to find someone that has actually done this swap to find out. Research adapter plates, and even go to a transmission shop and ask them about the mating of a small block to that transmission from the current engine.