454 to 350 swap questions

[K5anator]

So the ol 91 k5 has had it, the tranny went. She won't shift out of first or reverse. The floor is rotting faster than I can patch it back together. My body mounts are so bad my body line has quite the bow to it but hey it has 200+k of upstate ny winters under its belt.

So today I found myself a 87 c20 with 69k original miles but the owner says the 454 is set up its been sitting for 5 years. Ive had things sit 5 plus years and never had any lock up. My scout sat 20 plus years a lil gas and it fired right up. The motor is pulled so I can't test in the truck right now. But I am in need of a vehicle bad to get to work. My 350 runs great all I can find is 350 to 454 but I need a temp. Fix an ill build a nice 540 stroker over the winter.

So sense all the 454tbi wiring is there can I use any of it to plug in the 350 or do I have to swap everything. I want to put the 454 back in so I don't want to destroy anything. I believe the motor mounts line up correct me if I'm wrong the c20 has a 400 trans fitment wise I can just bolt it all up right.

I think I got it all figured out. Anything that may help me would be appreciated anything else i need to swap out. ill rebuild my 700r4 this winter and do a 4wd swap but until then I got to get this 350 in there

And I'm going thru the headache because the truck is super clean. Used to tow camper to Florida for the winter so it stayed away from the salt and got it for 1000$ thanks for the help

 

[diesel4me]

The 350 should bolt in using the same mounts provided your '91 is the old square body style like the '87...the flex plate should have a dual bolt pattern so it will bolt up to both TH350 and TH400 and 700R4 torque converters,so that should not be a problem,just make sure it does before you install the engine!..

The wiring is the same pretty much,as far as the distributor,starter,temp sending unit,etc,thats no big deal..the exhaust system may not fir the 350 manifolds though,at least the pipes coming off the manifolds will probably have to be changed..radiator hoses will probably need to be changed also..

I've installed 3 454;s in trucks in place of 350's and put a 400 small block in place of a 454,and it was a pretty much bolt in deal,just about everything was plug and play except for the exhaust,and I just made two elbows from parts stores to fit the manifolds and grafted them to the existing pipes..

 

[paratrooper307]

If you're using a 454 TBI setup to run a 350, you'll have to make sure you swap in the 350 injectors and ECM, as they are different.