Auxiliary Fuel Tanks in a C-20

[Happy_dan]

Greeting all. I was lucky enough with the help of a member here to have recently purchased a 68 C-20.

I don't see anything on the SPID about aux fuel tanks but there are two tanks extra tanks in the truck. They are installed in front of the rear wheels and fill from the rear wheel wells.

Are these original equipment or added after the sale?
There is a switch by the drivers seat that I assume is to switch between tanks. I don't plan on ever filling the tanks since the amount I will drive it will never use all that fuel.

When you switch tanks does the fuel gauge switch too?
There is some wiring under the bed (see picture) that I wonder if it was for adding a gauge?

Any information about these would be much appreciated. The truck is awesome. Just waiting on carb rebuidl kit so I can get it running right.

Happy to join the fray!

Lots of pictures here:
http://imageevent.com/happy_dan/dantoys/68c20