Aux fuel tanks: dealer installed? Worth keeping?

[DeadheadNM]

I'm mulling over what to do with a 72 K20 I recently picked up. The bed needs to be swapped out. The truck has dual bed mounted tanks and a three way selector on the driver side floor. Are these tanks typically dealer installed? Not sure if I should keep them for the resto I'm planning (i.e. install them on the other bed). The selector seems frozen but I'm reluctant to torque it too much. I'd appreciate your opinions. Thanks.