Triple fuel tank on a 1980 C30 dually

[D.B]

Originally Posted by Dillon Rock

So kind of like how the 73-75 trucks were with the manual selector valve on the left side of the seat? Also, for a 3 position rotary switch, if memory serves me right, that's a 6 pin connector vice 5 pin like the selector switch for the 6 port style from 77-80?

I think you are on to something.
I had a 69 GMC with three tanks. One behind the seat and two saddle tanks. I hated the manual valve and not knowing how much fuel I had once I switched off the main tank. So, I contacted a company that made rotary switches and explained to them what I wanted. They gave me a part number for a switch that worked. It was a dual-purpose rotary switch used to control the electric fuel pumps I put in the tanks. I also installed one-way check valves to keep fuel from being routed into the unused tanks.