Nickster,
I'm running a torquey 19T in my SC10. I used the bigger spur that came with the truck and a 25 pinion I beleive (will check tonight)
Anyways gearing will be different depending on the motor if its a torque motor like peak dinasty (black and green) or a more RPMish motor (Cameleon, Komodo dragon etc.) but in both case, since the brushed motor have more rpm than BL, you will need the big spur.