Re: rear fuel tank
I too wanted to increase my fuel capacity and was bummed to learn that Transfer Flow (TF) no longer sells the 46-gallon midship or smaller rear fuel tank to the general public. SMB West still sells the 46-gallon TF tank but they have to install it too for around $2,200. Too expensive to me for an extra 16 gallons of fuel that I'd only really need infrequently.
I think the least expensive option is to buy an aftermarket replacement rear gas tank which I've seen online for less than $200. Problem with that approach is you have to source and buy all the various hardware, hangers, fill assembly, and either route the fill to the existing fuel door, custom fab something inside the rear fender (like the old pickup dual tanks), or cut a new fuel door in the body. None of which really appealed to me.
An Aluminess rear bumper and three 5-gallon Spectre-type cans is looking better and better.
2007 Ford E350 PSD Quigley 4x4 and El Kapitan conversions, 315/70-17 BFGs