I welded a new rear floor pan in place and had to tie it in to the rear wheelwells. Of course, this meant I had to grind some paint to prep the area for welding, but I noticed that part of the wheelwell was covered with what looks like rubberized undercoating. A lot of it has flaked and peeled off, and the paint underneath matches the original exterior color. Did these cars come from the factory with undercoating in the wheelwells, or was that something that one of the previous owners might have sprayed in there?

Randy. My 66 had the same kind of coating.To me it looked like the old tar type of coating. The main function as I believe was soud deadening.

To my surprise the trunk side of the same panel, the one covered with spatter paint, had the same kind of tar like coating but with a flatter texture.

Hope this helps.

Rob