Master cylinder question

[Brooks James]

70;Dart factory Kelsey Hayes manual discs front, pirate Jack rear disc. I know that I want to use a modern 2 bolt master cylinder with an adapter and a adjustable proportioning valve
What I don't know is what size should the bore in the mc be?
I've read 7/8
15/16
1inch
??????

 

[Joey4speed]

Generally the 15/16ths seems to work best w manual front discs.
Not sure with your aftermarket rear discs.

 

[AJ/FormS]

I like my 15/16ths
I also have the KH 4-piston calipers on the front,
but drum rear brakes.
But I also have a booster.

 

[Inertia]

I run 15/16 on my builds and racecars, no booster .

 

[BillGrissom]

Dr Diff sells a 2-bolt MC for 1980's Dodge trucks, both standard and with a custom smaller bore (higher price, 15/16"D I recall), plus a 2 to 4 bolt adapter plate. On ebay I recall but linked here many times. I use an ABS MC from a late 1990's Breeze/Stratus/Cirrus w/ 7/8" bore as manual brakes in my 1964 Valiant. The Valiant pedal rod fit the piston (w/ new rubber bushing) and the pedal wound up in the same place (search post for photos).