Over the years, Chrysler vehicles were fitted with a number of different brake valves and combinations of valves. For the '67 model year, a dual master cylinder replaced the single master cylinder, and the brake system was separated from front to rear. A pressure differential valve was used to sense a loss of hydraulic pressure in either the front or rear half of the brake system and trip a switch, which illuminated the brake warning lamp and alerted the driver of a malfunction. Disc brake cars were fitted with an additional valve-called a proportioning valve-which limited the pressure to the rear brakes in an effort to control rear wheel lock-up on hard stops. By 1970, some systems used a third valve-called a metering valve-which blocked pressure to the front brakes until the rear brakes began to apply. By 1973, all these valves were built into one-a combination valve.
Taking all the pieces from one donor car for your conversion will simplify your installation and help avoid the possibility of installing incorrectly matched parts. It should also result in brake proportioning that's just about ideal. If you find either your front or rear wheels lock prematurely during a hard stop, you may want to consider installing a Mopar Performance adjustable proportioning valve. but there are a couple of other options. Installing rear wheel cylinders of a larger diameter will cause the rear brakes to apply harder, while installing smaller-diameter wheel cylinders will help correct premature rear wheel lock-up. If you're installing a single-piston, slider-type disc brake setup, you've got a third possible solution. While the outer dimensions of A-, B-, and F-Body sliding calipers are the same, A-Body calipers have smaller pistons. by installing B- or F-Body calipers on an A-Body, you could correct a rear wheel lock-up condition, while slightly reducing your brake pedal effort. Installing A-Body calipers on a B-Body could correct a front wheel lock-up problem, though this would increase pedal effort slightly.
On a final note, remember the front suspension must be aligned any time a front suspension component is replaced or disturbed. Otherwise, you could experience rapid and uneven tire wear, poor handling, and erratic braking.