cjoe,
If I understand it correctly, the switch would be rated for a certain amperage at a certain voltage. If they actually were rated, which they probably weren't, the 6 volt switch would be more stout than the 12 volt version.
I don't know what kind of load headlights draw, but the circuit should be fused, and it seems the switch should be rated at least as high as the wire, and higher than the fuse.
What all this means is too much current is flowing somewhere when you turn the lights on.
Try and find the fuse in the headlight circuit..make sure it isn't a penny. See what size the book calls for and install that as a safety for right now.
The least I would do is do some detective work on the harness that leads to both headlight assemblies. You might just turn up a crispy wire mashed under part of the sheet metal.
I guess you will have to replace the switch, so when that happens, you have another chance to troubleshoot the system. Does the switch have a parking light position, then a headlight position. Maybe a pot for dashlights too. You have three sources for a problem. Do each position at a time, let it sit and see what happens. If your proper fuse is in, it will save your $$$ switch. Let the popping fuse be your indicator of trouble.
Don't forget that the taillights are also on this circuit...mashed wires under a truck bed and around the tail gate area are not uncommon.
Good luck!
Stuart
