I have used mine so much that I already converted it to on-road.
Just ask Monster Mike. He should be able to replicate for you. Love the simplicity of the design. It has been BULLET proof.
The center diff is hard plastic and will need to be replaced soon. It is a cheap replacement via Red Cat part.
Got some aggressive spiked tires for it from ebaY. The MCD rally tires did not have enough grip. Jumps very well; totally controllable since it is electric.
Massive amounts of torque, so much so that she can act as a crawler. Not really my thing, but it is so much fun to see this giant thing climb some seriously steep hills.