I understand where you are comeing from, but I had to use an adapter on a stock replacement master cylinder. It was a little diffrent from my original master cylinder though, both reserviors were equal in size. The car could still easily lock up the front wheels though, so it worked just fine and is now on my '72 which came from the factory with a master cylinder identical to it.
Drum/drum m/c's are both equal sized. (worked ok on the mustang for about 3 yrs with granada discs on the front) When it went out I used a 75 mav. non power m/c and it works better than ever ( this took quite a bit of line work to use with the granada prop. valve)
On '74 Mavericks with all drums, they are not equal. My '74 Grabber had the original factory master cylinder on it when I got it.
