I personally would suggest using a higher Lipo setup, maybe with a Castle XL2. Since Power=Volts*Current, the greater the volts and amps, the greater your top speed. I don't think weight of the car should be an issue, it may reduce the acceleration, but not affect the top speed.
For the body, check these
http://www.stormerhobbies.com/cgi-bi...c=cs&pn=mca236
http://www.stormerhobbies.com/cgi-bi...c=ns&pn=MCA244