Well if you had the '70 Coronet FSM then you could have pointed out that I was wrong. Power to the dimmer switch does come through the H.L. Switch, but from the Stop and Tail Lamps fuse, not the Dome Lamp, as I had previously posted, and through a black wire pigtailed from the back of the H.L. Switch, other end pigtailed to a yellow w/ black tracer wire at back of Dimmer Switch. What's confusing about the FSM schematic is the multiple use of Pink Wires. Three different circuits use Pink as power wires, Parking Lamps- dimmable circuit, Windshield Wiper, and Brake- Dome Lamp( from the Hazard Flasher which also runs power to the Flasher Switch, opposite side of connector). And the Brake Lamps are on the Hazard Flasher fuse, not the Stop and Tail Lamps fuse.
The '70 Coronet FSM is not available for free download from MyMopar.com, and the schematic they have available pales in comparison to what's printed in the FSM.