You can run any servo in there. I'd recommend a Hitec or a Savox servo. There are some other really nice servos out there if you look around though. Tekin servos are really nice. It's 4wd, so I'd be looking at something like the Tekin T-360 if you want speed, or the T-440 if you want torque...
Oh man. That's a badwordhere nice one.
The only thing I see right off that I would want is a front bumper. I'd have that body shredded in no time I think.