Clone gear

IF it isn't a known track your best bet is to ask others there that already have a starting point. Gear it for whatever your engine builder recommends for the power range of the engine.
If you've tried the 16/63 & 17/66 gear combos and are still having R.P.M issues, YOU HAVE A TIRE ISSUE IF TIRES ARE NOT RIGHT YOU"LL CHASE GEARING TO THE COWS COME HOME.