Hi
The spur gear is an RW Racing 78t for the associated b4 thats what i've been using on my standard rb5 it is a direct fit no modifing just need associated slipper pads and it's cheaper than getting kyosho spur and slipper pads
The shell fits ok theres is abit of a gap like what you get on the standard rb5 shell and chassis and like i said i've cut mine below the cut line just to give abit more clearance
Paul