Upgrading to rear discs, need help deciding on a master cylinder!

[bmxmon]

Hello all, I don't post here much, just lurk. I have a question I can't seem to find an answer for anywhere!

First my car is a 65' Mustang with a Mustang II front suspension. I believe the brakes the kit came with (From Rod and Custom) are just your standard single piston GM caliper.

I just bought a rear end out of an 01' Ford Explorer for $150! Disc brakes, 3.73 gears, limited slip and 31 spline axles! Should work out pretty sweet for my end goal of a nice, mildly fast cruiser. (My Mustang will have a 5.3L Chevy and t56 in front of it)

What I need help figuring out is what piston bore and stroke I need for a master cylinder and if going power or manual brakes makes a difference. Hunting around I can't find any solid information. I don't expect an answer of "x" bore by "y" stroke, but a way to figure those values out would be great! I have yet to measure the piston size of the calipers, but I'm sure that is the key to it all.

Thanks for any help!