I recently started upgrading my truck, and one thing has led to another and I've come across a turnkey TBI 350. I have a 4.3 that I hate and nickel and dimeing me to death. I think she's fixing to go :-(. I just painted my truck, new head and tail lights, 31's, now I just gotta get a real motor in it. I'm new to this forum thing so bare with me. Any one have any advice on the engine swap?

 

It should be pretty straightforward, the 350 and 4.3 share the same block (obviously other then two less cylinders for the v6). The serpentine system can be used off the 4.3, just make sure you get the fan shroud for a v8 and a computer for that engine unless you want to retune the 4.3 PCM...

 

What about a wiring harness, will everything hook up okay, and do you know where I can get a new computer, would like to avoid a used one

 

These trucks haven't been made in almost 20 years... Not much you can do about finding a new PCM. If you want to upgrade and do tuning in the future I'd look into the ebl flash, I have that for my computer whenever I get around to putting my vortec long block/tbi 350 in my Scottsdale... Whenever that happens haha.
I'm not positive on the harness, some things may be different. Does your 350 come with one?

 

No it doesn't come with one, I should be able to get a painless. Does the computer have to be the same year as my truck, or just a tbi computer, or is flashing expensive?

 

I'm not sure, but I think it can be from 88-94... But obviously a computer for your model year is better. Just be sure that the truck is came from had an L05 tbi 350. The ebl flash is expensive up front but is a million times easier to work with the burning chips/proms for these archaic pcms. IMO don't waste your money on a painless, either use your harnes if it works or get one from the junkyard. Do you have an account on fullsizechevy? Go there and look for a guy named doober. He has a 92 (I think) stepside he swapped a 383 into from a 4.3. He can help you a lot

 

You need 350 radiator, fan shroud, and fan clutch, You need 350 motor mounts for the frame, the transmission is identical no change required, Your existing harness will work just fine it's all identical of course you will need a 350 throttle body and distributor, If you use stock exhaust manifolds me thinks even 4.3 y-pipe will bolt up been while since I've done one so kinda rusty.
Fuel pump is the same no need to change it but if you haven't now would be the time to do it to make sure the 350 runs as good as it can. The front accessories will bolt right up the suction discharge hose asm is a little short and will need to be bent as necessary if not just order one from 350 so it's not cobbled together.
Finally just hunt ebay for a pcm service number that match's yours but for a 350 the pcm is the same its the prom you need to grab.

Or since those computers are so terribly slow I always swap out to a 95 truck pcm of course there will be some harness mods involved but it's a much faster computer has better driveability and just a all around much better computer.

 

You will need 350 injectors as well