YAY! My Holy Grail parts arrived today. I actually found a set of NOS rear tail light/bumper upper and lower moldings for the car. The original lower molding was badly damaged by the giant "J.C. Whitney" rear bumper guards my Grandfather had installed for battle in Manhattan back in the 1970's. He retired undefeated (except for the self-inflicted, crush wounds on the aluminum molding.)
My next project will be removing the entire rear bumper assembly (all 100+ lbs. of it!) to swap out the moldings. The upper one screws in from the outside, no problem. But the lower molding is installed from behind and below and is completely concealed from access when installed on the car.
I can't say enough about Will McDonald Obsolete Parts in Rockport, IL.
https://mcdonaldparts.com/. I found him through a search of the part numbers and after falling down a rabbit hole of links, was able to find his website. I emailed him and within 10 minutes on a Tuesday night, he responded that he had the lower molding and sent me "proof of life" photos that verified he had the right piece. He told me a reasonable price $125 plus shipping in a PVC pipe, (an idea he actually recommended even before I had to).
While I had him on the phone, I asked if he had the upper molding as well: If I'm doing the surgery, I might as well replace both. (The two curved side moldings are fine, so I don't need those). He did a quick check and found the upper molding in his inventory as well for another $110. He was able to combine them in one 4'x4" PVC pipe. It just arrived today.
I can't tell you how long we have been looking for that lower molding. At least three and a half decades at last count! The puzzle was solved when I was able to stumble across a parts diagram last weekend that was mislabeled as a 1973 to 1979 bumper diagram and that was how I found the part numbers: D1VY-17C796 and D1VY-17C772. (1970 to 1973 used the same rear bumper).
While I'm at it, I might as well fix that one pesky tail lamp socket that keeps blinking in and out of service, since you also have to remove the bumper to pull the tail lamp housings.