Hi Greg
Cant help you with part numbers but I did look into the 6 speed option recently and my searches on this board took me to this thread:
Fitting 6 speed G50 to '89 Carrera
Dennis seemed to have made the most progress but he is still not finished. I PM'd him and he replied with an update and some pics, I dont really want to post that here without him knowing but PM me your email address and I will forward it onto you.
Good luck with the project - a lot of work to make it fit, I decided against taking it on.