Stop in for a cup of coffee

ZMan67S said

Turned out to be a wire of the portioning valve that would hook to a dash brake light that I don't have.

Click to expand...

Can't be right.
The prop valve has no wires, no switches, nothing 'lectric.
Only thing close is the brake 'safety switch'.
It's in the distribution block between the front and rear hydraulics.
1967 Chrysler Imperial Dual Hydraulic Brake System from the Master Technicians Service Conference Session 232

I *think* that wire is supposed to be held against the inner fender with a three-finger clip like the one on the alternator.
The connector just pushes on the threaded portion of the switch - just like the gas tank sender.
Inside, somehow it ties to the brake warning light. When the switch grounds, the light comes on.