Need some help on sticking a 5-speed in my car
 

I have a 70' Chevelle, engine will be a big block, size and HP still not sure but shooting for the 550-650 range.

So I have decided to swap over to a 5-speed or 6-speed and kinda confused on what I need to be looking for (what tranny) and parts needed to swap over to a clutch?

I think I am looking at a T56?

Where are the great places to get one?