You cant use a neu 1506 or 1509 they have 5mm shafts and there are no 5mm bore 48 pitch pinions out there, plus I don't even think you could get the larger diameter neu in there and if you could you wouldnt be able to move it around for gear changes. The rc10 is a little 2 wheel drive buggy that can't handle tons of power and even if it could..how would you control it?