If there's a cherry bomb on it, I guarantee that switch is for a 12v remote lead to an amplifier that used to be in the car. There is likely a 4,8, or 0g wire running under the door sills as well, that got left in the car...
I went to look at a '65 dart 4 door that was in almost the exact condition you just described - missing headliner, random switches, a custom radio in the glove box (not installed, just sitting in the glove box)
