I tried searching, according to the weld and sealant manual, there is no seam sealer along the exterior bottom edge of the rear 1/4 behind the rear wheel. All the pictures I've found (not many) seem to bear this out. of the pictures I've found, I don't know what the build date and plant is, either.
Would my October 29 64 Dearborn car have had any? Unfortunately I didn't document this area before disassembly/cleaning.