Spur and pinion gears are completely independent of the motor. As long as you keep the pitch the same between the two you will be fine. Make sure you start relatively close to the FDR thats recommended for your car.
The FDR is the final drive ratio. You find the FDR by dividing the number of teeth on the spur (large gear) by the pinion (small gear) then multiply by your transmission ratio. The transmission ratio can be found in your users manual. It is possible to not have a transmission so skip the multiplying if you don't have one.