From what I'm reading on this site and the others, there were two tanks avail: 25 & 31. I've read here that the 27 gal number is actually the 25 gal tank capacity plus the space in the filler neck. The 31 gallon tank is rumored to directly replace the 25 gallon model using the appropriate 31 gallon tank straps and sending unit, and you can continue to use the skid plate. My truck is rusted in the rear end, the tank isn't perfect, and the sending unit doesn't work. For around $225 shipped, all the parts including the tank can be at your door via rockauto. I just want to make sure I don't order something that doesn't work! I like to come here for a sanity check before I spend money!