Welcome to the land of TinyRC!
You should have posted on the Bit-Charg forum (Forums, then scroll down to Bit-Charg).
All Bit-Charg cars are the same underneath with some inner differences between the "booster" car and the "regular" Bit, so its basically a preference thing. This site has a shop ("Parts Shop" link above) and they're really good and friendly.
I'd continue, but really, this should be in the Bit forum. Go there and ask away!