72 Duster Resurrection

I'm guessing and betting 10" drums. That master cylinder in your pix looks like its as old as the car, and it looks like the 10" drum, or disc master in the catalog pix.

BTW i am also going to order the upper and lower ball joints for his car soon too. All 74 dart disc brake stuff. Lower ball joints left and right K781, K783, and upper ball joints K772. Then 10 years from now when the price has gone up and the available amount is dwindled they will be waiting to go in the corner of my shop.