How big of a tank do you need?
I saw an advertizement for transfer flow tank that will replace the stock fuel tank on a Mega Cab truck. This tank is a non-metallic tank just like the production tank is, so no rust issue with your fuel. I believe the capacity for this tank is 54 gallons? According to transfer flow this will work with the stock fuel gage and you do not have to open and valves to fill up the stock tank.
Just another thought.
The advertizement was in the latest issue of Diesel World.
I showed this to my DW and she said, I have spent enough on the truck and camper this year. So I might have to wait for next year.
Jim