There is two types. One with the "cosmetic" bead and then there is the "gaskets" or "seals".
I may be wrong but I don't think there were any factory trucks back then that had the "beads" on them.
My panel was original and like Denny said, its nothing more than #30 lb roofing paper. It was also between the fenders and body on my rear panel fenders but you can't see the stuff when the sheet metal is put together.
But, just like a lot of folks, since I'm not original I used some stuff that has the rubber, yes rubber not vinyl, bead on it. If anyone is interested the VW fender bead is good stuff as it does have a rubber bead and not vinyl....just info.
