Those vent windows on GM cars are rare finds. Junkyard only. And I the weather stripping isn't for sale anywhere for GM. Unless someone knows something I don't. I had good luck matching up the chevy truck grille from same year with my van one by using google images and LMC parts photos, and found my mine on there. I bought chrome trim for the truck and cut and bent it to fit on my front bumper above the grille.
Wow, I'm glad you linked steele rubber, didn't know about them. Just grabbed a hood to cowl weatherstrip and a windshield molding set. I bet the door weatherstrip and window felt kits I bought on LMC came from them.