Last year I replaced my quarter panel extension on my 1966 Chevelle. However, the light socket keeps coming out or when it's in, the light will be very bright (you can read the newspaper seveal feet away) and the turn signal doesn't blink. Once in a while I'll get in right so the light can function normally for a while. The reason I believe is a gasket or what I assume is a gasket. In my original extension, it had what appeared to be harden rubber rectangle inside the taillight housing surrounding where the socket holes were. This is msssing in my new one. However, when I look at the parts catalogs I see gaskets for inner taillight housing, taillight lens and taillights bezels (which I never remember ever seeing on my father's car). I was told the first one went between the extension and the quarter panel. I assume the lens one goes underneath the retaining ring and the the bezel one goes under the bezel. So, what exactly was that I saw in my original housing and where can I find it? Any help would be appreciated.

Sincerely,

Genaro