Installing Lt side full quarter panel on 70 challenger. Need to know what was used to fill gap of the seam where the quarter panel and the rear deck filler panel are attached. Was it seam sealer or something else? The gap for Rt quarter panel and rear deck filler panel still has the filler material. It is hard but that could be due to age. I ruled out lead because heat was not needed to melt the material to remove Lt quarter panel from deck panel. Any help would be appreciated.

Following, as im sure the same answer here will apply to my situation, a vertical seam on each side leading up to the windshield channel, 85 D150. Pulled windshield, cowl panel, and hood and saw a gap, whatever was used elsewhere on the cowl that hasn't fallen out is rock hard and falling away.