67 Valiant: brake problems. need help

the reason you couldn't remove the master cylinder is because the actuator rod (the rod from brake pedal to master cyl.) has a small O-ring deal on the master cyl. end that holds it in place and can sometimes be a pain to get loose. it simply pushes in and seats in the cup inside the master. give it a couple of good hard yanks and it should come out. replace it if it gets damaged.