E46 M3 and E39 M5 6 speed manuals are the same gearbox apart from having different bellhousings (which are interchangable anyway(
E36 328 and 3L M3 gearbox are the same but they are ZF and much tougher than the Getrag 6 speed E36 M3 Evo gearbox. John made bits of his Evo box
The E46/E39 Getrag 6 speed is a lot stronger than the E36 one as it has bigger shafts and stronger bearings but I'm not sure if its really worth it considering they are expensive and if you break it, your screwed whereas E36 5 speed boxes are plentiful and can be picked up for 150 quid or so.
I have an E46 M3 gearbox in my E30 318iS but its only a roadcar.
Also the fact that clutches are much easier to get for the E36 boxes as the splines are abit of a prick to get a clutch to suit on the E46 or E39 M5 boxes.
Your going to make bits of the layshafts and synchros on the E36 box to be honest as they aren't upto alot of abuse... but then again, the F20 won't have as much torque and its a realtively light car.
Going to be a sweet car once done!
