Well the prop valve should be on the that line. So it looks likethere is no proportioning valve on your car.
Correct - the rear brake line should go from the distribution block with the warning light switch, to the prop valve and then the hose with a Tee on the rear axle's vent. If you read the booklet, it explains the hydraulic pressure is not proportioned until something like 500 psi. So for light braking, whether it is present or not will not be noticed. At lower speed and dry pavement it will be harder to lock up than slick pavement and higher speed braking.
You can buy a texas shaped prop valve.
Yes, you can also buy a combo valve used on the later years. There are pictures of the same collection of Master Tech Bulletins. They are bigger and you'll not mistake them for the simple safety switch type.
That Master cylinder doesn't look correct. If it works, its only for the same reason the one you have works. They removed the residual valve.
All master cylinders for the a-body disk brakes used a bail retainer, not a bolt. There's a list on the last page of one of the master tech booklets.
All chrysler master cylinders use a different thread for the rear brake and front brake connections at the master cylinder.
Yea I know the brake light warning may be too late. LOL. But maybe in some cases it will help.