I run all big blocks but the 360 Crate engines are the ticket for you. If you buy used like you mentioned , just make sure you or someone knows the person selling it or knows the engine! Overdrive Trans sounds like a good choice but it may be tough with your budget. Just watch what you buy. There is a lot of junk out there. That is why I mentioned the crate engine. Look around, often guys start engines at machine shops and cannot afford to pick them up and the machine shop has to sale them.

Joe Sr