700R4 is an overdrive transmission and they do make them to fit the sbc... However, even some of the transmission shops have a problem getting them to hang together when you put horsepower to them, might not be a good one to learn on. IMO you'd be better off buying one from a reputable rebuilder put together with the pieces to handle the horsepower of the engine you're building and complete with a warranty. Even just setting the TVR cable wrong will smoke the tranny in a big hurry....