well my gear box has a lot of slop in it, mostly from the amount of milage one it

ive been thinking of replacing it and the rag joint but i figure if im doing a gear box may as well put a quick ratio one in

a buddie of mine has one from an iroc z camaro but its got 30,000 less miles than mine so my question is where cna i buy a rebuild kit of a gear box?

would a normal parts place carry it or is it special order from some where