GEAr RATIO
To calculate gear ratio : SPUR div PINION
To calculate final drive ratio: GEAR RATIO x TRANNY RATIO
So What ever car you get you must find out the tranny ratio.
EXAMPLE: TC3 tranny ratio 2.5
SPUR 100 div PINION 30=3.333=GR
GR 3.333 X TR=8.33=FDR
YOU then use FINAL DRIVE ratio to figure rollout
HOPE THIS HELPS