Are we talking all out speed or race worthty? The outlaw, back street, for big money guys around here run hyper 7s with .32s and tall gears. They lock the center diffs and let 'em rip. The only one that hits curbs and still keeps going. One guy has a 1/5 scale, chain saw motor, if he doesn't rip tires off, is in the money. Great fun to see.