Another ZX5-SP newbie

[90dug]

Hi Guys
Been lurking for a while and with all the reviews gone and got myself a ZX5-SP. I race touring cars at the mo and used to race off-road years ago.
Anyway back to the topic i have also got a 5.5 brushless to go in.What pinion would you recomend with stock spur.i have some yokomo ceramic diff balls to go in insted of stock ones.
Any other build tips??

Thanks in advance for the replys

Simon