Gasoline is probably the most dangerous common substance we all come in regular contact with. It sure makes me nervous to see these solutions. I pull a 4X8 utility trailer with a custom made 50 gallon tank mounted over the axle of the trailer - in the U.S.

Over here in OZ, there are long range tanks made for some of the Pajero models. They are expensive and I imagine the shipping to the U.S. would be prohibitive. In most areas here, fuel tanks mounted externally are illegal. Diesels have better range, of course, but that doesn't help you.

I used to figure 100 miles in 4WD on my 2.6L Monteros. Finally finding a V6 Raider helped a lot with better mileage an a larger tank. I don't have a good answer, but I repeat; those solutions sure make me nervous.