Hey. That trim seal can be gotten from almost any GM parts place. It's the same seal for any A-body GM. Cutlass, Skylark, LeMans/GTO, Chevelle.
Leo Konik, ausleys, ground up, opgi, year one, soft seal, etc
But first I would look at the deal Rob Peters has with metro moulded. It's in the General 70-72 Monte Carlo area.
Hope this helps.