there is a much simpler way but I don't feel like thinking.
plug in your numbers to BrianG's speed calc for the e-maxx trans
http://www.scriptasylum.com/rc_speed/index.html
find your top speed. then trial and error pinion teeth until you match the desired top speed.
also I need you to make me two sets of lst diff to maxx bulk adapters. One for me and one for the PIF maxx. PM will come eventually................