it is an ATTA Tank -
Mine isn't really what I would call custom - other than I had them add a 2nd filler neck.
I'm in Houston Tx area.

most of ATTA's tanks are built to order - so modifications are easily incorporated - great folks to work with.

When I did this years ago I considered KSH Marine too...but they were considerably more expensive as I recall.

I used their Freedom Fill system - did the install myself - Freedom Fill automatically kicks on the aux tank pump when the factory gauge reaches 1/4 (remaining) .....the aux pump runs until the truck tank is about 3/4 (or slightly more) full...and shuts off. The FILLING cycle repeats until the aux tank is empty (the aux tank has its own fuel level gauge)....and a switch to over-ride/shut off the aux pump.