Those black rubber seals on the 66-70 and 71-74 B body (and E body) fresh air vent doors is "over-molded" onto the steel door. It's not replaceable. I get so many requests for these seals that I buy a dozen or so of these vents every year when I'm at the shows so I can help customers looking for them. 1/2 the ones I get are usually pulled away/delaminated from the steel but they can usually be glued back down. It's pretty rare that they are destroyed or "eaten by rodents".

That must have been you that I sold the vent to yesterday. Small Mopar world. Glad I could help. For chap the vent may not have been pristine but the door was the best one I had.