feigao 8L gearing

what are some ways to keep the motor and esc kool without choppin up the body????what would be a good set diffs????what if i just went the hobby shop and got the traxxas diff spool for it???? what kind of gearing where you running in your truck to hit 50+mph, squeeforever????tell what you think if i got these cells from a battery site i found:
http://www.all-battery.com/index.asp...OD&ProdID=1661