I've read that there are more differences between the Mega and the BLX than just motor and esc, like driveshafts, steering links etc. Some stated that a Mega would break within seconds if you just install a 3s combo?
Motor plate is plastic on the Mega and aluminum on the 3S BLX. Pinion and spur gear pitch is different on the Typhon, Granite, Senton mega, no center driveshafts support on the LWB cars, etc.