Novak is pretty much the only way to go for racing right now. The LRP works very well and is smaller but has not demonstrated nearly the reliability that the Novak GTB setup has. The Mamba is very good too but can have cogging problems since it is not sensored. Go with the Novak and don't look back. 8.5 or 7.5 max for 2wd buggy, 7.5 or 6.5 for truck (6.5 is still a little much) and 6.5 for 4wd.