Power Disc conversion/ proportioning valve question

Not sure if bench bleed applies to this type of Master Cylinder.
It absolutely does. Also, make sure that your bleeder petcocks are at the highest point of whichever item you're bleeding. I have to unbolt my calipers to rotate the bleeder to the top to get the last bit of air out of them.

Don't forget that Mopar drum brakes are self adjusting, too. All you have to do is get the car rolling backwards about 10 to 15 MPH and firmly press the brakes a couple times. Depending on how far out the adjusters are, you may have to do this multiple times. That is, if they are assembled correctly.