Hey i have a 305 with busted crankshaft and would like to swap it out for a smaller mor economical V6. Will the engine mounts n electrical, tach, speedomiter oil pressure.. work or how much extra work is it?

I bought this truck new and it now has 266+K on it and the engine is running very rough when it runs at all. I know cylinder 2 has 60 lbs and the rest are at 120-125. I would like to swap out the engine for another 4.3 from another year if that is possible. What are my options?

I just got a 91 chevy s10 4.3liter v6 and i want to know what i should start with first to making it an everyday driver but with plenty of power.