If the car is stopping as well as you say, then you may be forcing a non essential problem that isn't a safety issue with excessive pressure at rest.

Your factory proportioning valve may need replaced with an adjustable modern valve where you aren't overpowering the drum brakes. Which end locks up first? If your brakes are functioning properly, your fronts should lock up first.

I have to admit to hooking up the lines in reverse on my master cylinder--the whole front-to-front thing is easy to sell. The reality is of course big (pot)-to-front, and small-to-rear. It's really hard to tell in effect, short of your brakes completely sucking . . . The original poster does not seem to have this problem.