I am running 16/87 gear. I chose that just because that was the pinion that I had on hand. I have an 18t pinion here also that I can try. I tried to use the other spur (75 I think? don't have it right here in front of me) and it would not work with pinions I had (the holes didn't line up). From half throttle the truck takes 10 to 12 feet to stop. It will not lock up the rear tires either.
Thanks!