search man.

for the most part the k20a2 is a good candidate and there is alot of aftermarket support for this motor. The k20z1 is a bit stronger but will require you to do a little modifying to the speed sensor. The k20a is BY FAR the best one but the most expensive one. Check out hybrid racing, R-Crew, hasport, chasebays, etc. This should get you started.