My heater system was completly useless on my 1960 Chevy pickup due to the cables being utterly seized up. I decided that defrost is a necessary thing lately as we have been having -21 temps lately. Anyway, to the point, my truck has the heater blower on the engine side of the firewall and blows heat into the interior through a cool little duct system. The medium by which this duct attaches to the firewall is an old black thick foamy kind of gasket. I can't find this gasket material at any of the automotive places here in town. I can obtain thick cork gaskets, but I'm not sure if cork will work in this application. Anyone have any idea where to find the original thick foamy gasket material or if cork is suitable for this application?