I bought a truck one time that had a manual tank swap switch under the seat that you had to reach under the seat to change tanks. They had removed the spare tank out of the bed and plugged the fitting to the valve before I got the truck but someone had switched the valve over to a position where the fuel from the stock tank behind the sea didn't flow. Took me a day and a half to track that one down and to the "Oh @#$" and laugh a bit.
I don't much like an electric actuated switch as you still have to have power in the system or a secondary system to have it work. manual switches like some of these
https://www.speedwaymotors.com/Searc...ion%20Switches That are normally used on race cars would work if they were hidden and it shouldn't be that hard to figure out a way to operate one with a push/pull cable. Push or pull a know on or under the cash to engage the switch or disengage it and you have a hidden setup that you can operate with someone in the seat beside you not really catching on most of the time. Pull the cable just before hitting the switch or have it over to the drivers side where you pull or push it with your left hand and no one even pays attention to what you did. Switch could be mounted on the firewall with the contacts on the outside and the lever on the inside with a small box over the connections on the outside where a cable ran in and out but wasn't much noticeable.