The Nikko Thunderbolt was sold with 380 and 540 motors. The 540 motor version was a 35T or 45T motor: 12600 rpm at 7.4V and 1.3A no load current y the car has full proportional control electronics.
I have tried to put a 27T motor (Johnson "silvercan" motor of Tamiya) of 18,000 rpm and 1.6A no load current. The original electronics do not overheat.
The original electronics have a "H-bridge" of bipolar transistors: 2SA1129 (pnp) and 2SC2654 (npn). These transistors have a maximum current Ic = 7A and drive a peak of 15A.
The collector-emitter saturation voltage of these transistors is Vce-sat = 0.3V at Ic = 3A or
Vce-sat = 0.6V at Ic = 5A, so the motor is powered between 0.6 or 1.2V less than the battery voltage.
The motor speed is lower than the same car with ESC (electronic speed controller) of Mosfet transistors.
In spanish lang. in http://reparar-cochesrc.blogspot.com/2020/01/cambio-de-motor-nikko-thunderbolt.html