Ford's drawings usually show the gasket as part of their exploded views with a part number. It's not there. It's also not in the 68 body assembly manual. I don't dispute your having them, it's that there is no documentation supporting them now. A called a friend with a 67 A code Fastback (May 67, San Jose, he found it in a field near Oakland, CA about 10 years ago) and he says that there was no gasket in his and that he used strip calk to put the drain housings in.
Jim