I've run a couple different GM hydroboost units. I first one I ran back in 2009 was from a 1-ton GM truck/van which was 1-1/4" or 1.25" bore. Pedal travel was very short and I could easily push past it in an emergency situation. Just scary. IIRC I switched to a Camaro unit which is 1-1/8" or 1.125" like
@baldilocks and thats what I've run since then. I believe I've seen people switch from 1.125" to a 1-1/16" or 1.0625" bore and made an improvement on that. That was on a FJ60 with 1-ton/14-bolt axles. That Wildwood is much nicer to look at than mine!