The RPM is limited to 30.000 due the ignition system. The huge torque makes it possible to use a different gearing but you do need to have such gears to make it competive.

In the 1/10 there are some conversions to 4-stroke which do come with different gears, the OS FS26c is most used. In the 1/8 buggy you can find conversions with the OS FS40c
http://www.rctech.net/forum/offroad-...opment-83.html

And there are also diesel conversions.
http://www.davisdieseldevelopment.com/index.htm