Actually looking at it now and being a boat builder and knowing how big those fills are and the fact that it is only an 18gal tank its not that big correct? It would be ok in the back of your XJ as long as it is vented correctly (the 3/4 barb) and bonded to earth ground. It says bond to earth ground for a reason... The fill hose is to be wraped in a 10g wire and bonded to the chasis. If you dont and your jeep is hit by lightning which isn't uncommon "BOOM"... Thats why it says that.