It very well could be a Dodge vs Plymouth thing. The lady at the Auto body store suggested I try their generic clips like the one you had posted. So I supposed if someone had pulled the trim to paint it they could have used those. Or in my case when most of the trim was in the trunk you are left to fend for clips and screws. I also noticed you edited your original posting. Didn't it say Coronet 440 before? I have a few 65 500's with the skinnier trim I can check to see what fasteners they use for the those. Pretty sure I tossed most of my 440 trim last month.