Here's the details on the custom tanks for those of you who may be interested... .
My tanks are for my '08 shortbed, but the changes necessary for a longbed are minimal. These carry a full 30 gallons each, and I estimate that the longbed version would hold about 40 gallons each. I made a model of the tanks to insure fit into the bed, and made the construction drawings from the model after I was sure that everything was correct.
The tanks are made of 1/8" thick aluminum, with two baffles in each tank. They have unvented caps, and a check-valve vent to allow air to enter the tank as the fuel is drained out. The tanks are transfer tanks which are plumbed into the factory tank through individual solenoids. Since the tanks fit over the wheel hump, they each need 2 drains in the bottom, one forward and one to the rear of the hump. I plumbed the 2 drains for each tank together, and then tee'd that line to a solenoid valve. The plumbing is symmetrical, and as a result, each tank will have the same level of fuel, and the front and rear of each tank would be exactly the same level, as well. The lines from each of the tanks are tee'd together to provide a common "dump" to the factory tank.
I installed a vent kit to the factory tank to allow faster and more complete filling [That mod really works well... . it only takes about a minute to obtain a complete fill in the factory Dodge tank. ] Anyway, I used the origanal factory vent line to be used as the fill line for the aux. tanks, and that works well.
I tried to find a local fabricator here in Tucson to do the fabrication for me, but wasn't able to find someone who wanted to the job. I found a marine tank fabricator on the internet in Florida who was happy to do the job.
The tanks weren't cheap, but considering the way they turned out, I'm not unhappy with the results. The pair of tanks from the fabricator were about $1400, plus another $150-$200 for the tank caps, filler necks, and threaded weldable inserts. Add about $200 for Line-X.
I'm a retired engineer, and had a ball putting the project together and bringing the project to fruition. I'm not interested in patenting my design, or in any profits associated with marketing the design. I think that it is an interesting design, and anyone else who wants to have a similar set of tanks fabricated for their truck is welcome to use the plans.
I've tinkered with Auto-Cad and that's the software I used to make the drawings. If anyone would like a copy of the drawings and has the ability to read Auto-Cad, I can email the file to them. If they would like a set of printed drawings, I will be happy to mail those to anyone interested in having them. Please send requests to -- email address removed --.
I will be happy to provide additional photos and answer questions on the construction details to anybody who contacts me via my email.