I have not seen one of these in about 40 years so I am going to speak in generalities and maybe it will help you.
Electrically, I see what you are talking about on the distributor ground lead, but, I am pretty sure this is not used and the ground is made thru the carburetor and it's attachment to the intake. Power is fed from a switched ignition source that energizes the solenoid when the key is ON.
It's easy enuf to test that...ground the case and apply power to the lead coming out of the solenoid. Plunger should jump out a little.
On the set up, crank the engine up, warm it up, and then set the idle by adjusting the screw that touches, or should touch, the end of the solenoid plunger until you get to 950 rpm.
Now, the screw they refer to as the curb idle screw...they say to adjust it until it touches the
Throttle Body and then back off one turn. I believe that screw is on the opposite side of the carb where the throttle linkage from the accelerator pedal is attached (what normally would be the idle adjusting screw). Turn it until it makes contact. At this point, if you turn it further, the idle would increase beyond the 950 rpm that you set at the solenoid plunger....instead, you back it off one turn(this does not affect the idle because you set it at the plunger).
Now, when you turn the key off, the plunger retracts and the screw that you backed off one turn now becomes the idle speed screw and allows the throttle blades to close a bit further cutting off most of the air to engine and preventing after run or dieseling.
The book's instructions are very unclear. I hope mine are right
I remember that was how most cars worked.
