200 or 212mm setups work w/ either of the NA trannies... only real difference is you will need either the plate that covers the bell housing... or fab up something to cover the exposed "ear"... beyond that the trannies swap no prob... dont even have to remove the clutch set
I've rebuilt a C52 and added an LSD. I think I remember that the fifth gear replacement and upgrade parts on both C50 and C52 are the same, but I don't know how much different the main internals are between the two. I suspect there is very little difference. I used the C52 to get the intake starter position for the ZE.
I agree with Mark. If you have a limited budget, definately get one from a salvage yard, or someone off the board.
BTW, to replacing fifth gear parts to solve the infamous pop out problem will probably cost $300+. You can do this job with the tranny on the car and a gear puller. You can also find a used tranny in the same price range. Your choice.