[Andy4639]

You will need a new controller, solenoid, charger and the per say motor will need to be replaced more than likely. The stock regan motors are not acceptable to higher voltage with out mods.
U can buy a alltrax controller with the regan effect but I doubt u use it much.
72 volts would be easier to do for charger and controller's. The alltrax are all good for 48 through 72, but what I have found is they like the max voltage better than any other setting.
Good luck with it.