M20's are more solid than you think.
assure your bottom end is good, and at the very least replace your HG and freshen up the top end+headbolts.
conservative boost at 8psi and you can still run on your stock ecu, beside BMWConnect is the local go to guy for boost tuning.
I have a build thread over on MR for my turbo e30, lots of knowledge here too Everlast has a very clean setup.
start parts hoarding/collecting
read this--> http://www.e30tech.com/forum/showthread.php?t=74816
also Ryan George over in the F/I section of max has a good turbo M20 write too