I am going electric, and this is the motor & gearbox I am hoping to use:
Neil Blanchard Designs: Rumination on Electric Drivetrain for CarBEN EV5
This is an AC induction motor with typical 95% efficiency. No permanent magnets, so virtually no drag during coasting. It is water cooled, as far as I know.
The 6.4:1 reduction differential is with no changes in the axis of rotation, and the left side output shaft passes through the inside of the motor; which has a tube for it's shaft. In total it weight a bit less than 79kg (174 pounds).