Does Master cylinder bore size really make a difference.

Someone mentioned cylinder area. That is very easy to figure. But there MAY be another factor. You take one off, you slap on another. BUT YOU MAY possibly have JUST SLIGHTLY changed the leverage. WHAT?? How. Because "maybe" the new cylinder has a slightly different depth at the rear. This changes the pedal in it's arc, and the pedal leverage CHANGES as it goes through that arc. Pedal leverage is going to be maximum when the pedal is effectively at 90 degrees to the pushrod. If it's either up or down from that, the arc will cause a change in that advantage.

Mine had 9", manual brakes, and the factory cylinder. You could squal all for tires at 70. But you could not do that very many times!!! Brake fade. I have no idea what type of lining were on them.

When I had the first "white whale", the 1/2T 2WD Dodge, 97? I forget. It stopped "fair." I read online about fooling with cylinder size and calipers. I believe 3/4T calipers and on a 1/2T pickup. Turned that thing from stopping fair into something that would put you right through the windshield.