While it's not engine related, it is paramount to the build up of the wagon.
When I ordered my 4x4Labs rear bumper, I asked that it be made to fit the Long Ranger aux. fuel tank. Luke Porter is a genius. Without having a tank in house, he moved the rear cross member back so that the top hangers for the tank would bolt onto it instead of the factory supplied brackets included with the tank.
Here's a picture of the tank and bumper before it was fitted onto the truck. We were able to fab about a 3/4 inch spacer to raise the rear of the tank up for some added ground clearance (Bonus). The tank was then coated with a hardening "Bed Liner" type spray paint before the install.