Here is a couple of good ones..
http://www3.towerhobbies.com/cgi-bin...?&I=LXRUN7&P=0
http://www3.towerhobbies.com/cgi-bin...?&I=LXPRL2&P=0
http://www3.towerhobbies.com/cgi-bin...?&I=LXHTN0&P=V ( this is the stock one)
The hard thing is finding a rotor carb and for a racing motor there going to be fast no matter what.