Get the transtar one yes, but makes sure you get the high performance one with kevlar clutchs. They make 2 HP kits. One by Borg-Warner and one by Rybestos. Either will work. It has green clutchs. If your going to rebuild you need to view the list of to do things. Final drive, Hp overhaul, silonoid pack, shift kit. Might want to consider a high stall around 2800 convertor, also buying the upgraded planet set. Its a huge improvment. You can also buy a lsd like the obx or quaiffe, as there worm gear driven, and not crappy slip in types. Even do the wiring mods

There is alot of unlockable potential in these little trannys. I have about 2k invested in mine. yeah Im crazy, Yes it would have been much cheaper to go 5 speed, But I like the feel of an atx car way better and for me it was well worth it.