I like the prolines road rage but they are too wide.
Better going with something like this as Mike suggested:
http://www.amainhobbies.com/product_...ith-Inner-GT-2

BTW I took the truck for a test run and there was a little cogging but barely perceptible. Went up to 11,000 RPM which was about 23 MPH and felt crazy fast but I loved how the front was lifting without loosing contact with the ground.