a racer like me then...
get some E-revo diffs at the least, center diff with some really heavy weight diff oil (the nitro revo center diff is a little too weak for my taste)
IMO i like what i have done and used a E-maxx 3905 tranny, loads stronger.
use mikes.s gearing calculator (google "rc calculations") and one of the first few will have a top speed estimator thing.
use that and gear your car for 40mph, that is almost garenteed to keep things cool enuff.
i have mine geared for 40mph and my temps are never over 130 on the motor :) running 5s :)
good luck in beefing it up.
shaun