Okay Sentra, there seems to be some confusion here. Just to clear things up Here is a list of GM style automatic transmissions.
Power Glide (Older 2 speed, still the choice of many drag racers)
TH-350 (3 speed, CHEAP and strong will hold up to what you want if built)
TH-400 (3 speed, Heavy duty version of the TH-350. More weight and power loss but much stronger)
200R4 (4 speed overdrive, kind of like a TH-350 with overdrive. They are getting hard to find)
700R4 (4 speed overdrive, Kind of like the TH-400 with overdrive. Probably most popular for swap)
If you are wanting to bracket race with your car I would suggest an automatic. It is very hard (if not impossible) to be competitive in a manual. The swap also seems a little more simple with an automatic as well. I am going with an auto myself but that is just because I cant afford a T-56 six speed. Mine will be a street car.