55.2-59 59 GMC 270-336 swap.

[dsraven]

if you're doing a numbers match truck, then, hey, do what you gotta do. if doing what needs to be done to get it going and running so you can drive it, then, hey, for me, an ls swap is the answer. easy start, good fuel economy, pretty easy to find a donor truck with everything you need, no carb issues, etc etc. it is the new small block replacement. back in the day everybody was swapping a sbc into the spot where the old tired engine lived. nowadays it's the ls engine. keep the old stuff and don't torch things apart so you can still go back to stock. oil up the parts and keep the old stuff on a pallet in case you wanna sell it someday. it can be put back to stock if wanted, on somebody else's tab. but today, with the fuel prices like they are, and the parts hard to find, a fuel injected engine and ccomputer controlled trans from a late model donor is the way I would go. thats just me, if you wanna do the old truck thing then that is you. your call. a numbers match truck is gonna be expensive because they look at everything. a half done numbers match doesn't really make the mark from the numbers match perspective so, what the heck. do what is gonna work for you, keep all the old parts. doesn't seem like using a really old "good running engine" is the most economical way to go since it may give out on you at any time.
this is just my opinion. it is your truck and your pocket book. you do what you want to do. just giving my 2 cents. think about it, if a buddy of yours showed up with an old truck and he said "yeah, it is all stock except the driveline because it is so expensive to do an old engine so I installed a 5.3 LS engine and an automatic trans from a late model truck in there and I kept all the original stuff on a pallet". would you fault him? he is driving it and having fun, right?

[daveshilling]

Originally Posted by dsraven

if you're doing a numbers match truck, then, hey, do what you gotta do. if doing what needs to be done to get it going and running so you can drive it, then, hey, for me, an ls swap is the answer

It's my answer too, but it's a slippery slope. You need to change fuel delivery, so probably an EFI system with the tank under the bed. You make new fuel lines now. You change the wiring. You need to change the mounts. You need a new oil pain I would guess, You are probably getting an auto trans, and you probably had a manual before, so you may need to change your shifting mechanism. You need to change your driveshaft to a custom piece. You need to change the radiator most likely (might need to anyways)

Your gauges are useless now, so you'll need to change those.

You'll have way more power now I bet, so you'll probably need a disc brake upgrade to handle slowing down as fast as you speed up. So you'll need a new master, and probably a booster while you're there, some way to mount that, prop valves, residual valves, etc. You'll need a couple new brake lines then, too. (I would argue do disc regardless but still).

OR

You can drop in a 336 that was meant to be there, and change much, much less. Update the fuel line, some throttle linkage, maybe move the trans mount depending on what ya stick in there. You also don't need to learn about all the little things that need to be updated and spend $18 on some little thing you need like 25 times.

[dsraven]

there is also the tried and true small block option. prolly easy enough to find mounts, manifolds, bellhousing, etc etc.
up to you. I just don't see the economics in spending money on an engine that is not common. I would, personally, cut my losses and swap somethghing common in there. thats me though. it is your truck and your dream so you need to build it like you want it. no looking back.
I suggest to look at all the things that would need to be done.
fuel system, do you wanna keep a fuel tank in the cab, right behind you? fumes, leakage, etc.
exhaust, is the current system viable or will it need to be replaced anyway
wiring, are you good at wiring to be passable should you wanna swap in a sbc or an LS engine
trans/clutch, is the current clutch and trans good to go with the different "old" engine or will that need some work
rad, will the current rad work with the different "old" engine
engine mounts, will the current engine mounts work with the different "old" engine or do they need an upgrade
bellhousing and rear mounts, will the current stuuf work with the different "old" engine or will there need to be cash spent
gauges, what will work
linkages

I guess what I'm saying is do a complete feasability study on doing the upgrade to swap in the 'old" engine compared to upgrading to something modern, or more modern. do the math and decide. a few hundred for this, a few hundred for that, new hoses, flush rad, new clutch, pretty soon you have a good sized bill to install an old partially worn out engine that may work out well or may start burning oil and leaking oil shortly after you start using it. not trying to be a downer here, just trying to give insight and help you make an informed decision.

[72 k15]

Suppose I should have updated the thread, I found out my old 270 is good and am rebuilding it now going to keep the truck stock other then a sm319 which you wont see. I just figured it would be pretty obius its not a v8 truck if you looked at the vin plate. Not a whole lot of these GMC's with original engines still so I think that would be nice to see.

[dsraven]

well it's good to hear you have it figured out. maybe post up some pics so we can all see the project.

[daveshilling]

Originally Posted by 72 k15

Suppose I should have updated the thread, I found out my old 270 is good and am rebuilding it now going to keep the truck stock other then a sm319 which you wont see. I just figured it would be pretty obius its not a v8 truck if you looked at the vin plate. Not a whole lot of these GMC's with original engines still so I think that would be nice to see.

True, the first thing I do when I see a cool truck is ask to inspect the VIN plate

Glad you're getting her on the road!!

[72 k15]

Yeah truck actually runs and drives well, I just hate the auto choke on the 235 and it leaks a lot. So if anyone wants a good running 235 let me know.