HELP! Engine and transmission compatability

I am about to buy an 80s El Camino and don't know which years the engine and tranny will fit into. Please help me out as the body on this is crap but the engine and tranny are good. I plan on buying a 72 or older El Camino without engine/tranny and dropping this in.

Please help... I need to get this before tomorrow morning if I am going to. After that it will be gone.

Nevermind everyone. I have decided that the 305 is smaller than I want.