Im thinking about getting a 1987 s10 blazer. It has a 2.8L v6, I was wondering could I swap it and put a 3.4L v6 and not have to change anything

 

3.4L?? How about a 4.3L "Z" engine? Anything can be done, but there would be a serious amount of work and parts retro fitting involved in this project. It would include multiple wire harnesses, PCM, fuel pump, (probably fuel tank as well) engine sensors, etc etc etc. Better have stock in Tylenol and Advil too