Just to throw in some useful info for people searching this thread in the future…if you have a front disc/rear drum brake system make sure the master cylinder you buy has a residual pressure valve in the rear brake circuit. If you don’t have one every time you lift off the brakes the rear shoes will retract, meaning you have to take up that slack again when you depress the pedal. I tore apart my brake system several times until I finally figured out this was the problem. The Dorman (and probably many other) master cylinders listed for a 68 w/ power disc/drum do not have a residual pressure valve. The only one I know for sure that does is the Raybestos model (which unfortunately I believe they have discontinued). Here’s a link to my thread on this with more info and part numbers: Sprucing up a '68 Cougar - #123 by mfc133