What is the type of hose you're using for your fill-line? I've seen a couple people have it but not sure what it is and I'm thinking I would use it too since everybody else is lolI have a 350HD (dually) and I used the 31 gallon over the wheel well tank from North West conversions. Also framed it in using 8020 10 series. The thicker your floor insulation the closer you can get it to the wall of the van. Far from perfect, but I still thought it better than a standard tank. To give me access to the fittings I traced and cut out a 3/4" plywood of the bottom of the tank raising it up a little more. I have a raised bed platform configuration, so I can store mountain bikes and other gear. Not sure if it would work with your build, but thought you would like knowing it has been done with a dually. This configuration the tank is also in the galley cabinet area (not done yet in this photo). View attachment 182493
12/6/22 EDIT: nvm, I found it: Amazon.com