I think your doing great. enjoy following along

What if the Packard ‘star wheel’ adjuster is too long for the shoes that you are using? I’m not saying the adjuster is too long, but the shoe itself has too much material in that area. We know the thickness of the shoe’s web was too thick for the stock Packard adjuster, and you took care of that be thinning the web. If there was also too much material facing toward the adjuster, then the net result is a shoe diameter that will not fit into the drum. In that location of the shoe we need about 1/8 inch ‘more adjustment, that’s about 1/16 inch on each shoe, but 1/8 on each shoe would allow a bit of extra slack.

On to the photograph of the master cylinder plumbing entering and exiting the distribution block. I think that’s all it is, a distribution block with a ‘brake system malfunction’ switch. If either side fails a piston under the switch shuttles to one side and a dash light comes on. I think the geometry is such it will not automatically reset, but others may fill-in details. If the light is hooked-up it makes bleeding the brakes a pain.