64pitch is a very fine tooth count. Pretty sure that's typically used in smaller, mini sized stuff.
Gear pitch is a way to tell how many teeth are on a gear per given inch of the circumference of the gear. The gear pitch for any nitro I've seen is called Mod1. So as long as your clutchbell is...
AFAIK all nitro gears are all Mod1 gears. Someone can correct me if I'm wrong but everyone I've ever owned were all Mod1 so just make sure you spurs are Mod1 and they should be fine with your clutchbell