the first connector I had in my Electro-Willys was made from the center of an old clutch. It slid on easy and had a little wiggle room. With use, and the torque from the motor, it contributed to breaking my motor shaft off inside the motor. VERY EXPENSIVE REPAIR!!!! Part of the problem was the less-than-perfect allignment on the adapter plate holding the motor to the bell housing. The motor shaft needs to be pointing straight at the input shaft, or any little wobble will begin to spin it off center and begin to tear it apart.
I went back to the flywheel and clutch. That is working very well, and it's a ton easier on the transmission for shifting.