Drag Car Master Cylinder and ADJ Proportion Valve

Hi
I am building a 72 duster drag car with a stroker 400. I upgraded the front to the larger 73 and up brake setup and I am running a narrowed 8 3/4 rear axle with rear disc brakes. I bought the rear disc brake kit that uses the gm calipers (I believe they are cadillac deville or something like that).

The car is back halfed ladder bar. Given the larger disc brakes and the disc brakes in the rear what manual master cylinder size should I go with? The largest 1.125? Anyone have auto parts store part numbers or vehicle applications so I can find one local?

Also any recommendations for an adjustable proportion valve given the setup on my car?

Thanks!!

Seems like that would be correct, but is *** backwards, if its manual brake set up , u need a smaller piston master cyl.. I have a 15/16 master cyl on mine , have thot about a 7/8 , but I`m not having that big a problem , 29.5 tall tires on the back, 26 on the front , no proportioning valve , just the stock 4 wheel drum deal .