That is a trail and error thing. Are you running a tach. If not you need to. To see what your max rpm is at end of straight. You will gear it to hit per say 6000 rpm at end of straight. And this will not garantee they won't beat you off the corners. Depends also on how strong your motor is compared to them, how well you are setting up for the turns compared to them in relation to how ealry you are getting back on the throttle compared to them. Many variables there. Want more pull go dwon a gear or go smaller on motor pully or bigger on transaxle pully but doing this takes away from top end. Thats why you need a tach to adjust it to said rpm so you know for sure what the engine is doing.
George