[RC-Monster Mike]

Depends on the wind(Kv is determined by the windings, not the magnet). Pretty sure a Feigao or Hacker shaft would fit right in, but there are some issues to this theory. The best for that motor would be a Hacker rotor(make sure proper clearance from shaft to windings), with a 5mm shaft. I say use your current motor's shaft and keep the pinion closer to the motor can when you mount it to avoid the potential for a broken shaft(most times, the shaft is broken due to high stress when the pinion is mounted way out on the end of the shaft-leverage will win!).