[hatzie]

Originally Posted by rich weyand

I put dual tanks on my 78 and used the motorized valve. It fits the existing mechanical holes in the frame, and the existing fuel and vent lines. It will switch the sender wire if you want; I ran both sender wires to the dash and have a gauge on each, one in the clock position and one under the tach.

To power it you need two wires back to the valve from a switch that reverses power and ground wires. Power I took from the IGN position in the fuse block, ground I took from the ground buss bar located at the parking brake pedal bracket under the dash. I mounted the switch -- which came with the valve -- in a pre-existing hole in the bottom lip of the dash to the right of the steering wheel.

You can see the switch in this shot, currently set to RHS tank.

Toggle switches are a heckuva lot more reliable than the plastic rocker switches and you can make the bat point to the tank being selected.
Cole Hersee makes a Polarity Reversing toggle switch that can use the same connector housing as the 73-80 GM rocker... but not the wiring.
Cole Hersee 55018-01 Polarity Reversing ON-ON toggle switch with blade disconnects