I'm currently in the process of building a 71 and although I'm not at the stage of a trans, I'm trying to plan my attack. My plan is a street car with an appearance at the track every now and then. I'm shooting for 400-450 hp from my motor, so the million dollar question is, what is the best O/D for my car, and what do I need to hook it up? I don't know much about the difference btw a 700r4 and a 4L60 or 80 trans. All input and advise would be appreciated.