First look at the single speed E-Maxx conversion kit

[RC-Monster Mike]

I would use the recommended gearing for the Novak system, as well as the fan. For mounting the motor, I would mount it low to one side-opposite the steering servo is where I put it(I don't use shift servo), high enough to clear the controller, but as low as possible.
You will want to use the fan, or you risk thermal shutdown, especially on a hot day.