pinions and spur
 

I will be running slipperential, hb diffs, quark, quark heatsink,fans, and 7xl what size pinion and spur should i run to get fast speeds but still be efficint for every day running and racing(run cool and realiable), i also dont want it to be over or under geared. also i will be runing . The reason i am asking is because i do not want to just buy 200 dollars in pinions before i find the right gearing so if you could tell me what would be good it would save me cash. Your opinion is greatly appreciated. Thanks