What Bore Master Cylinder Do I Need?

So after figuring out that most all the boosters have the same "spread" I am looking at a GM dual 7" booster with correct aluminum master. Now where I get stuck is the bore.

Currently running stock LBP 73+ discs and 10" drums. MY plan shortly is to go to the B Body 11.75 rotors with Wilwood calipers, with the jeep rear discs, with 18x9's with 255/40-18's on 4 corners, basically protouring.

I was looking at a 1.25 bore as i'll have half as much surface area on the new booster (75.6) than the stock single 8" (50.2).

Thoughts?