Thanks for the info supernova, I've found the Lynch motor website and am having a look now.

A pancake motor would be a decent choice, I could mount the motor on a frame below the engine, use a toothed belt to perform the reduction and have a long drive-shaft to connect down the space where the motor is now.

Thanks for the info on planetary gearboxes typhoon_driver, do you happen to know if they can be driven backwards instead of as a reducer?

I shouldn't have believed the website that said overvolting the Magmotor wasn't a problem, direct-drive was nice and simple though