I wouldn't make an off-road car with that pinion. All that top-end you'd never see would be a real waste compared to how fast you could take that on a smooth surface, provided you have the force to get you there. For off-road applications, what you want is a few-tooth pinion that gets up and goes immediately; not one that takes some running room to get up there.
But, it's your project.
That looks like the same size as the XMODS motors, but there's no way I can tell if you'd need FETs or not just by looking at it. How much current does it want?