Rarest A-Body Option?
I had a 71 Dart Swinger /6 car, typical except the interior had a Kleenex brand tissue holder that sat on the center hump under the ashtray. There was a metal clip that fit through the carpet and the tissue holder slid down over that. I've never seen another one and it was the same pale yellow as the interior. The same car also had a rear speaker with fader switch, separate under dash map lights and a rear DEFOGGER.
I think there is a difference between the blower motor system, which I refer to as a defogger and the defroster, which was available probably in 74, that consisted of the wires on the rear window that heat like the modern defrosters we have today.
I have a defogger on my 70 340 car and I have an extra one I can take pictures of if you guys want to see it. It used a package tray with the slits cut out for one speaker on the drivers side with no special grate. This is where the motor was mounted, in the speaker location and the center vent was long and thin. If you had both the rear speaker and the defogger, the speaker was on the passenger side (at least it was in my 71 Dart).