Anyone know the diameter of the transmission end of the alignment shaft? I think I have the aluminum plate that goes on the helmet, I also have a shaft but it's not fitting in the transmission well. I may have to make a shaft or an adapter. This is the speed master 3/4/5 application.

you may be able to measure diameter on the low side of the splines on the drive

transmission end diameter is just under 1-1/8", 1.110-1.115 should do it