A 1/10 scale crawler that CAN'T take a 550 or 540? That ain't very good, in fact, my 1/14 scale buggy comes with a 550 brushed motor (yes, the stock power to weight is pretty good)! What kind of motor are you supposed to use, a 390 (brushed) or 28__ (brushless) size motor then?
In crawling, you don't need crazy speed, as most of the time your crawler will be going <5mph. As such, even with the low gearing, the motor won't be churning out tons of RPMs, which also means that efficiency is still pretty good, and the motor won't get hot.
Brushed motors don't suffer from...