yeah, I seen that, but it's a start I guess. are you talking about the gasket behind the headlight bucket against the fender? I don't recall a rubber seal between the bezel and the headlight. possibly all the trucks I have worked on have been missing that peice. I am assuming there is a rubber between the bezel, the metal part that has the big hole in it where the headlight pokes through, and the headlight sealed beam part. maybe you could post a couple of pics of the parts you have. mine have all been bare steel headlight bezels.
possibly this site has a better pic if you scroll down. it's for the passenger cars but probably GM didn't change a lot of things between cars and trucks when talking about the little mundane things like this. anyway, you could check if that is sorta the same thing.
https://www.trifive.com/threads/57-c...estion.180796/
here os a link to a brothers video that is for the AD trucks but possibly has some reference to the TF trucks too. it shows that rubber gasket being installed in the bezel.
https://www.google.ca/search?q=1955+...IAi9URwplfEVgM