Jim,,, I bought the tail light gaskets that are on the market now,,, they are way thick and made of some foam like material... i went ahead and installed them any way... and they did not look right at all.... so....
I took the tail lights out and cleaned the flanges real good and used black rtv silicone stuff that i bought at home depot....... put it on the flanges of the lights about 3/8 or so thick ,,let it set up completely untill the next day.... then put them back in the car,,,, they pulled up nice and tight and looked like a factory installation....hope this helps.....