If you looking are for a GM manual box, do yourself a favour and stay away from the Muncie 5 speed from the 1980's. There are some still at swap meets.
I put a Buick 3.8 litre in a Triumph TR-7 ragtop in the mid 90's and the Muncie box was simply crap. They were noted to be a crappy shifting tranny on the down shift. Completely vague to would not let you into 2nd gear. I found this out later and had to drop an autobox in instead.