There was a guy on e-bay selling all types of gaskets made from original patterns.
He contacted me once when I was parting a 63 Polara and wanted to buy all the gaskets, like tail light foam and master cylinder gaskets, ect.
Just found them
Detroit Muscle Technologies
https://www.ebay.com/itm/DMT-Mopar-...g-Turn-Signal-Light-Lamp-Gaskets/290637882675
That’s Jim Filmore, he is very focused on doing stuff 100% right or not at all... I restored my first couple cars back in the 80’s, I bought the reproduction body gasket kits & was so disappointed in the complete lack of quality that I reused every original gasket I could... That continued through the 90’s.. In the early 2000’s timeframe Jim was restoring his 71 R/T, he bought the reproduction body gasket set & like me was appalled at the crap we were being sold.... Un like me, he had the ability to do something about it... He worked as a engineer in Detroit for a company that supports the auto industry by supplying weatherstripping & body gaskets...
Initially he just made a few small runs of gaskets for his particular body style Mopar... He sold a few gaskets, I was one of the guys who bought his product before it was really a product...
Everyone raved about the quality & Jim decided to expand, he bought some equipment, started talking with suppliers about exactly what materials were originally used, he started asking to borrow tail lights, marker lights, parking lights etc...
By taking precise measurements off the light rather that the gasket he assures the gasket fits the housing rather than duplicate a gasket that had shrunk over 50 years...
Anyway lots more to the story including buying his own building in Detroit to manufacture products...
If you haven’t bought from Jim you should... If there’s something you need that he doesn’t offer ask, he’s always looking for new products..
Jim & Loretta Filmore
Detroit Musclecar Technologies
https://www.detroitmuscletechnologies.com/