I don't know why you were searching a long time. It's been posted many times here and it's on Grid's web site. As you found you need a Mod1 pinion. Grid recommends (and I've used) Hot Bodies pinions (as you correctly stated, they must be short shank) If you use the external support, you have fewer pinion choices (max size is something like 19T, but don't quote me on that).
Originally Posted by
Sarinexia
Been looking for the answer to this question for a long time. A straight forward, simple answer. I'll put out my findings:
Grid RC - Motor Mount for RC8be.
Yay! Great upgrade. What size pinion?
Answer: Mod 1 5mm any tooth (depending your set up) should, SHOULD work.
Here's my choice (19t).
http://www3.towerhobbies.com/cgi-bin...0&I=LXXKB4&P=K
OH, and it has to be short shank. At least if your buying the inner mount from what I know.