Hi Norm
When I was using an FC the previous owner had roughly ground down an FC boss to fit in a recess in the auto pulley. Even though I am not using an FC I machined an FC boss to fit just in case I have to go that way.
Rough as it was it worked OK, no real vibration etc. I am using the same pulley up the other way with the PT.
No idea what the auto pulley came off though.
All the best
Jeff