if you got hit hard enough to rupture an in-cab tank, you wouldn't be alive to worry about a possible fire, a ruptured tank and ensuing [possible] fire is way down the list of things that could kill or maim you and your passengers in any old truck .... I've been driving old trucks for decades and have seen the remains of many fatality related ones, most had windshields shattered from the inside, or the steering column was 3 feet further back than the factory put it, or any number of other cab "modifications" like drastically lowered roofs, but none were burned
if you really want a tank under the center of the truck, find a panel or burb tank and mount it there as the factory did
anything is possible, but your thought, money, and effort are better spent on more probable risks, and safe driving is way up there, as well as careful constant maintenance
Bill
