Well, I think I figured it out. I was misreading my VOM at the generator box when the shore power was connected. It was reading 120mv (not volts). It is dark and cramped inside the compartment where the box is ... that's my excuse anyway.
It appears that the generator electrical box wires run to the 30a receptacle in the shore power cord storage area. As a manual transfer method, I simply plug the shore power cord into that 30a receptacle if a generator is providing power. In my case, I plan to connect my inverter output to those wires instead of a generator.
I just have to remember to turn off the converter so I don't charge my batteries with the inverter when it becomes the power source.