Heads up to those that install a 2 bolt aluminum master cylinder.

The 1 1/8" bore is large, I agree.
Dr Diff suggested this for the use with a hydroboost setup that I was first working with. I couldn't get the HB working so I tried a 15/16" manual setup. That didn't feel right so I'm back with the power booster. I figured that if the 1 1/8" unit was right for the hydroboost, it should work with the vacuum booster. If it results in a weird pedal feel, I still have the 15/16" unit to try.