http://www.bmwhaus.ie/forum/showthread.php?tid=1353

http://www.bmw-driver.net/forum/showthread.php?t=78369

A small case would be ideal if you can get one.
M3 diff will work as is (medium case)
Evo will require full rear change. (large case)

Car will be slower due to m3 diffs and lower in the rev range. I have a small case 3.64 in my car and it sits at 3k revs at 60mph and 3.5k revs at 80mph. Acceleration is also improved.

med or large case are easier to find and more resilient than the small case.

Also the gear box should bolt straight on. Lads even run 316i boxes with an IS engine as it's a quicker ratio supposedly.