I dont know what your gearing is and if 1 speed or 2, but MMM/2200kv- 4s in a Kyosho gt wont go nearly as fast as the nitro versions, he will be going high 40's .. I agree with Bdebde, throw a 6s /25c-30c/5000mah. Hit high 60 low 70s easy .. Gear for 100+mph speed runs...
Gotta measure your battery tray to find what will fit
http://progressiverc.com/6S_Lipo.html