Your '73 never had a proportioning valve, and it's likely you wouldn't need one unless swapping to front disc brakes. Your pedal going to-the-floor is likely the result of a worn out master cylinder. You should have left the hard lines alone (unless they were rusted) and you never should have needed adapters to make anything fit. There are only 4 things that can cause your pedal to go to the floor: 1. Leaking flex-hoses (2 front and 1 rear). 2. Leaking wheel cylinders. 3. Leaking or worn-out master cylinder, 4. Air in the system. (I didn't mention calipers, because I assume your car has the stock brake system)
A lot of people call the distribution block a proportioning valve. In Mav's and comets, the Distribution block has the brake warning light switch mounted in the top of it.
