My headlight switch is (apparently) not working although I haven't tried it personally so I have yet to check mine... that's just what 4ontheFloor said when he did his inspection, but he felt the switch could be dirty so ya never know...
I'm leaning seriously in favor of 6V myself since she is pretty much original and will have a look at my favorite battery places this weekend to see if they offer a good 6V variety at a good price... Once a healthy battery is in the truck it should be much easier to diagnose any little problems that may exist...

~Trev