r/Squarebody

Hi everybody! I've been toying with an engine swap in my '86 and I'd like to get some feed back on my options, see what kind of experience some of you have and can share. I've got this '86 K20 that my dad was having built. He bought it as a shade tree 'restoration', and it ended up being a mess. So, he had someone rebuild the brakes, fuel system, suspension, and steering, and install a brand new TH400. The engine has burned oil since he bought it and kept saying, "It just needs valve guides." Well, I didn't believe that and scoped the engine. Oh boy, chipped pistons, blown head gasket, deep scoring in the cylinders, and a ton of carbon is what I found. I honestly doubt the engine is salvageable because the scoring is so deep. So, I was thinking about another 350, since that would be an easy swap. But Marketplace doesn't inspire much confidence, to say the least, and I'm concerned any "ran when pulled three years ago" engine is going to be a cracked or worse $400 boat anchor.

Now I'm looking for other options. I could go with a crate engine, but they too have their common issues, and as this is still more of a work truck, I'd rather not spend $6k on an engine. Another option is to pick up a good running, but well used, GMT800 Denali and pulling the 6.0 out of that. I'd like to keep the new TH400, so I don't need a truck with a 4L80E. I could also get a 2500HD drivetrain with the 4L80E, but that becomes a far bigger and costlier project, since I would need a new transmission cross member and new driveshafts for the longer transmission, and the donor truck is a lot more expensive.

Here's where I'm looking for a little help. If I go with another 350, how high can I go with gearing before it becomes unbearably slow? '80s 350s are not known for power.... If I go to a 6.0, would the extra power make 3.23/3.42 gears livable? I'd really love to use the truck to go Pull A Part digging but that means I have to highway it. The 4.10s it has now don't allow me to do that; it'll start running hot above 58.....

Let's be real, it would be a lot cheaper to just buy a GMT800 half ton to do my junkyard travels with, but as nice as they are, square bodies are a lot cooler. And who knows how long a used 4L60E is going to last, since they are not known for being the most stout transmission ever made. And we all know a $3,500 truck can be the worst $10k you can spend.

Edit: I forgot to add that I have a 32.5 inch tires on the truck, stock suspension and axles.

Also, I didn't touch on the options like short/blocks and reman units. I guess I've been scared away more recently due to a lot of horror stories since 2020. ATK, Jasper, and Blueprint have been named on quite a few forum posts for poor longevity. But, as we all know, squeaky wheels get the grease, and it seems the Internet has made squeaky wheels so much louder. Please share feedback, if you can, on short/long block options, as that really would be the easiest option.

If I end up with a short block, and buy some of my own parts to build a solid performer, would that be something where I could go to those 3.42 gears?

So I’m looking to buy my first square body since it’s probably my dream truck, but what are some tips for buying one? Like, what should I look for when buying one? I’m mainly looking for one that has 4x4 and a 350 in it. I already know rust is a big issue with these trucks, so what rust is good and what rust is bad? Also what are some common issues that would make you walk away from one instantly? I’m not looking for a perfect truck, so normal cosmetic rust or small repairs that need to be done to it are fine. I just want something I can drive and have fun with.

I have a Chevy K10 with a Certified Transmissions rebuilt 700r4/4l60e. I have put about 20,000 miles on it and then towed a 4Runner on a car trailer. Not knowing any better I used OD. After towing, the transmission shifts just fine, but once I start climbing a hill with the cruise set, it will try to downshift to 3rd but will make the truck shake and surge until I let off the throttle. The internet doesn’t give me a definite answer so I’m coming here!

Hello! Looking for a little insight. Ive had my blazer for less than a year and have been on a fun tinkering journey. But there’s an awful lot I don’t know.
The small belt that powers my smog pump and ties into the fan wore out and broke yesterday. I drove home after removing it with no problems or concerns. I picked up a replacement and got it on there but there was an awful noise when I started. Worse than a loose belt squeal. I didn’t have anyone else’s eyes to look at what was happening and didn’t want it to run that way any longer than necessary. I’m thinking the smog pump might be seized up. My question is, long term, what could go wrong if I don’t get a belt back on there and have a functional smog pump? Again it’s an 88 k5. Thanks!