Brakes problem
1965 Ford Mustang 6 cyl Two Wheel Drive Automatic 130000 miles

Hi I have replaced everything on the brakes except metal lines and proportioning valve. The brake pedal is up with very little travel not spongey. feels good but it just slows car down. I have bred the brakes several times no air. Oh and these are not power and all drum single cylinder master cylinder.I'm thinking rust in line. I have never had a proportioning valve go bad on anything before. I am not able to get the metal lines lose at the valve without cutting them. so I'm hesitant to try