Stupid question of the day!

Thanks for the info and the pics everyone. I figured it must be an optional thing.

It's wired (according to the diagram) exactly as 67Dart273 said... power from the same fuse as the rear window defrost, through the light and ground at the switch.

Interestingly, it's not shown on the '66 Dart diagram I have. Maybe Mopar gave up on the idea for a while?