using drum MC on front disc setup

Mattax said
Sadly, the parts store master cylinders are often drum brake MC's with one residual valve removed. In other words you don't get the casting with the larger resevior. Does it work? Sure. I'm using one right now. Ideal? No. OldManMopar explained the reasons Chrysler didn't do it that way..

True, a lot of the parts listings fail to discriminate correctly between the drum and disk MCs, particularly for the years 67-69. But all A, B and E body MCs are bolt-in interchangeable, so you can certainly find the right big&little reservoir type, just by trying different years and models.