confusion over distrobution/proportioning block

A distribution block per se is NOT the same as a prop valve that happens to be incorporated such that it also "distributes" the tubing. The clue PHYSICALLY (I'm not talking about a "stock" photo---) is that a DRUM distro block is always symmetrical, and the prop valves are always very much lopsided looking like the photo you referenced.

Some installations used a separate metering valve.........one line in and one line out

Below is a drum system distro block. Notice the symmetrical appearance compared to the prop valve

db_20060723_pics_0071-jpg.jpg

Some help might be if you go over to MyMopar and download the 70--72--73 service manuals and look through them. I have found some reference online that some cars also used a prop valve PLUS a metering valve. I cannot confirm that as factory as I simply don't have info on that