It seems like you need to read up and look at a factory service manual car for a 73-up brake system, so you can see how the lines are routed. I think you can find it at mymopar.com. Some simple thoughts are, do you have a master cylinder for a 73 A body with disc brakes? Are the bleeder valves at the top of the caliper? If you use an adjustable proportioning valve, it goes in the line to the rear brakes. I personally like a stock style prop valve. Keeps everything the way it was designed from the factory.