1971 Plymouth 'Cuda 440-6 power brakes with stock front disc, rear drum.

Both of my front brakes seem to be locking up. The car drives and stops fine.   I can't feel the brakes drag and the car does not pull to one side or the other when I apply the brakes or when cruising. I noticed a lot of brake dust on the front wheels so I jacked the front end of my car up and both front wheels where really hard to spin by hand, like really hard.   Both rear wheels are fine. The parts that are new or freshly overhauled: power booster, master cylinder, both calipers, discs and pads. At that point, I replaced the master cylinder with a different overhauled one.   Same problem. If I let the car set for a while, the pressure lets off until I drive the car again. Any ideas?


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