Please Help! Cannot find gasket to seal tank to bowl.
 

The connection area where the tank bolts to the bowl is recessed and when I bolt it on the bottom of the tank is making direct contact with the lip of the recessed area. (see picture) There are no markings anywhere on this toilet to determine the brand. The only marking is "August 1979" on the inside of the tank. Anyone have any ideas on how to get this sucker to seal?

Replace the gasket. You'll have to settle for a universal kit from the hardware store if you can't get the specific brand.

That should take a standard foam gasket.