Whats size pinion should I get?

[BrianG]

54T spur? This must be 32 pitch, not the stock Mod1.

There is no such thing as a pinion that is too big. The final drive ratio is what matters, and of course if it physically fits. I'm running 40T spur and 14T pinion (mod1), which would be like running a 19T pinion on a 54T spur. But, I am running wide ratio second gear, so, 22T on 54T is pretty close to what I am running FDR-wise. You should be just fine, especially running a Neu. However, if you want a little flexibility, I would get a 19T and a 22T just so you have some options.