Another trick I learned from the booster rebuilder was… booster laying on its back, set the rod along with disc in position. Wrap a rubber band around the studs and rod to hold it in place. Mount the booster. Remove the band and mount the MC.

Just wanted to finish this thread up.

The rubber disc was in fact missing and floating around inside. I had to use my borescope and a bolt grabber thingy to get it out.

Pedal travel is much better but the brakes still need bleeding. Its at the shop now getting done.

It happens a lot more than you would think.