One critical part that needs to be fabricated is a coupler that connects the motor's output shaft to the Alfa flywheel. This part needs to be a precise length in order to hold the flywheel in the same relative location in the bell housing as it was with the gas engine. The coupler must also firmly attach to the motor, which led me to a few design iterations. Most motor couplers I have seen utilize the 1/4" key on the motor shaft. Some people add a set screw to apply pressure on the key stock to keep everything in place, others machine the coupler to have an interference fit that must be heated to install. Both of these methods seem less than awesome. My engineer buddy suggested I look at a Trantorque keyless bushing to make the coupling. These nifty devices expand inward and outward as you tighten the nut. The Trantorque can handle 360 lb/ft of torque, plenty for this application!
Once the Trantorque is tightened to spec, a bushing is pressed in that holds the pilot bearing. The coupler is pretty much a permanent component that would only be removed if the motor goes kaboom.