The 1000 Watt motor is better off the line and will provide a higher top speed than the 750 Watt motor.
There are no 36 Volt motors that will mount directly on the original motors mounting holes without adjustment. Our MOT-36350 36 Volt 350 Watt motor will fit the original motor's mounting holes however its sprocket sticks out a little further than the original motor's sprocket does so the mounting holes would need to be filed or drilled to reposition the motor. The 750 Watt and 1000 Watt motors mounting bases are larger than the 250 Watt and 350 Watt motor's mounting bases so their mounting holes will not line up with the originals and new holes would need to be drilled or an adapter plate made.
If you are using the original controller then its motor connector will be plug-and-play with the 750 Watt and 1000 Watt motors.
Please let us know if we missed any question or if you have any new questions.