So maybe 10-12 ? years ago I decided to change the brake booster. The MC was leaking and brake fluid naturally did a nice job of causing the paint to bubble and get all rusty/crusty. I found a NORS booster on ebay and installed it along with a fresh MC at the time. About 10 days ago I started hearing a little vacuum leak, next day I pushed the pedal down and noticed it went away... Pulled back on the pedal and all hell broke loose. Super obnoxious vacuum leak formed and only goes away partially if I push the pedal.

Front end brake servicing was already on the schedule. I was going to be doing calipers and hoses (going to the LH calipers) in addition to the rotors/pads ect. Since the booster has failed and requires the master cylinder to be disturbed I might as well just change the MC as well and call it all fresh. Pretty sure I'll be making new lines from the MC to the prop valve. I got all the nice tools for doing that now anyways... I have re-made brake lines for everyone else and everything else but my own car

My memory is foggy on the debate but I did order a 15/16" / 24mm master cylinder. Pretty sure that is what I have now and it seems to work. Trying the AC delco 'professional' flavor this time, it claims to be aluminum like the original chrysler unit. The current unit is cast iron.