Not only will you probably have to make some moutns to fit with the e21 mounts, the speedometer cable has no outlet, not to mention reverse switch, output shafts, etc. If you're going to do it, you're definitely going to want to use the 5 speed from the later e21 (80-up) They're a dime a dozen. If you have an e30 five speed and that's why you want to use it, you could sell it and probably buy 3 e21 5 speeds. Hope this helps! -alan 83 320i 79 320i