Power Brakes Issue
If you are gonna get something like that just go to your local parts store. That appears the same as the original 67 in my car
Lowdown on masters "generally" speaking
You want to lean towards smaller, "manual" bore which gives you more pedal leverage
The only actual difference between drum / disc is that the reservoir for the front brakes, which is the rear of the master, is larger to hold more fluid. THIS IS NOT NECESSARY for day to day driving. All you need do is check the fluid regularly, as the pads wear
Second, drum brake masters normally have little valves called residual pressure valves in the outlet ports.
I'm actually using that or a similar master you posted, which is the actual original 67 in my car, to operate FOUR wheel disk brakes. I have 73/ 74 Duster brakes up front, and a Linc Versaille 9" Ferd with factory disk in the rear
All I did was to use a nail and puncture the two residual valves