[Christ]

You may also be able to shave some of the length off the e-motor you want to use, by pulling the end plates and milling them down. Leave enough meat for the bearings, though.

The Siemens E-Bike that OCC built, they had to remove and mill the plates several times to get it aligned and centered properly above the swingarm bracket, so it didn't bind the belt at all. Look for ways that you can shorten up the motor.

If there's a second housing bolted on the top that contains a cooling fan (not likely), you can probably remove it and use liquid cooling, which will save you some length, as well.