I have one that's still in the heater box. It's from a 74 Duster but should be the same. I can remove it sometime tomorrow & check to see if it works.
I'll get some pix too, if any interest in it.
I believe the '73 + attach with 3 studs and is sealed from the inside, whereas the '72 would be mounted with 4 studs and be sealed on the outside with a collar.