I bought a 71 Demon, 318 car with 7 1/4 and drum brakes recently and without asking alot of questions, installed a set of front KH brakes. I did not change the master cylinder and prop brake. The brakes work but not very good and the pedal is very hard and the car does not stop wac.

Besides the mistake of not changing the MC and Prop valve, is there any other issues i have created?

What is the easiest way to change the prop valve

ideas and suggestions welcome.