I have a 1998 Chevrolet 1/2 ton truck with a 350 5.7L Vortec engine, when I bought the truck the engine had a dropped rod and is way beyond repair. My question is can I use an older engine with the same displacement and bore and everything (a 1991 350 TBI and just put my Vortec intake manifold/heads and make a Vortec? Will every thing line up? What all do I have to change? I have got no answers from other sites. Please help.
It appears that the heads on your engine may not match the bolt pattern of the older engine.
To be sure you can go to your local salvage yard and they can cross reference certain parts like the heads and intake to see if they can be swapped.
Also check your auto parts store and maybe they can match up the two different year cylinder head gaskets to see if it will be able to be done.
My advice is to find an engine that will match the one you are trying to fix (same year) so you don't have to worry about swapping parts and possibly having to modify anything along the way.