I think dad's '77 F350 had that with the electric switch, but the fun one was my '74 Bronco which had a mechanical control valve located on the front of the driver's seat floor platform. Whenever the engine started sputtering, I had to reach down and rotate the lever 180 degrees to switch tanks. Then flip the switch on the dash to make the gauge read the other tank. Forget to flip that switch to check the level on the other tank and you'd be hoofing it.
