i HIGHLY recommend you either a.) get pinion depth tool$$$$$$ or b.) go to someone to install it who has one! i have heard alot of people using motorsport gears and throwing them in by using backlash only. i did that myself. so later if found it was making a noise. sent it to a guy who does gears witht the tool and he said i was lucky i didnt wear an abnormal groove in the gears. i was close on the coast and drive side, but way off when he compared it to when he installed.
if you are still going to tackle it, here is some useful info:
http://www.corral.net/tech/drivetrain/gears.html