You have [link=http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=ntc3+pinion&FVPROFIL=++]these[/link] gears to choose from if you get that threaded bell. I'm not sure if you're going to be able to adjust the engine mount far enough to make that 27t pinion fit. It will take some experimentation. Use the Evader BX spur gear - it's smaller.