how to keep mm 5700 cooler

[t-maxxracer32]

ok guys well my motor is getting somewhat hott now with the a123 cells and i was thinking if i bought the rcm heat sink it will help. but it wont fit the stock tranny case so if i bought the flm tranny case would that help with the cooling( the fact that its aluminum) gearing is 87/18 and i know i need to get a smaller pinion and thats why im pordering one! what pinion do you think i should get?

lmk what i can do to help out with the heat problem!