All of the cars so far have disc brake master cylinders. You can tell because they have a big reservoir and a small reservoir. The drum masters will have equal size reservoirs.
JeffC,
That's what I thought as well, but here's a 1971 Duster parts car in my backyard, I can't swear that it's correct but it looks like the original and runs, drives, stops normally, it is a power drum brake car.
I think it was probably replaced at some point with the wrong master cylinder. I'm sure it stops fine I dont think the extra volume of fluid would effect the way the drum brakes work.
I myself had a 69 Dart that was converted to front disc and I ran the drum brake master for a few years. It stopped good you just had to step on the pedal harder than normal.
