I have a 58gallon aftermarket tank in the 7.3 gas f250 I drive. I couldn't imagine going back to the factory tank. It's very nice when you are driving backroads all day a long ways from any gas stations.
I placed an order directly with Grohman knives. After waiting a month I got impatient and canceled my order and placed a order through one of their dealers in canada. I had my knife in hand in a week or so.