I was not aware that sixpacks ever came with a retard solenoid. I bought mine from a friend, and knew it's history. It was a 4 speed and came factory with a cast iron, Presolite dual point, no retard solenoid. It did have an idle speed solenoid on the throttle
(The wiring diagram does show 440-6 with retard so they must have)
However, the manual is contradictory. Even though the wiring diagram shows a retard solenoid for the 440-6, the tune up specs clearly indicate dual point settings, so ??
The functions of the two are not related, except that the "knub" on the idle solenoid which hits the throttle is the "switch" for the retard solenoid. Not all cars had idle solenoids. My friend had a Holley 4bbl equipped 70 GTX 4 speed, which had a switch made up of the idle screw on the carb, which was in an insulated assembly.
The throttle lever would come down onto the idle speed screw, which was insulated, and ground the screw. The wire off the idle screw assembly would then ground the retard solenoid at idle
The idle speed solenoid was simply hooked to switched ignition. It's job was to provide a higher speed idle to meet smog requirements, but to dump the throttle blades clear shut when the key was shut off in order to prevent "dieseling" or run-on
A quick look in the fuel section on Holley 4160 4bbl seems to indicate that stick cars came with an idle solenoid, and autos did not. This means the carb (photo below) had the odd insulated idle speed screw