Factory seam sealer??

The quarter panel seam was leaded up until around 71 then they switched to body filler. The leaded ones do not have the rot problem the later ones do. For the other seam sealer in the car they used at least three different types. There was the "foamy" type used around the cowl seams and under the top edge of the fender. They had one type that was similar to what is typically available now. Third was a thick rubber/tar type used a lot in the trunk area and floor pans.