There is a guy on dieselplace who has a super low dually w/ a gooseneck still in the bed. I will try to find a link to that thread later.

I would really have to sit down and do a cost breakdown to see just how much more economical the diesel is. I get ~14-16 driving around town, 10-12 pulling a bumper pull w/ scotti's buggy at about 70, and ~8 now pulling a heavy load (25,000 +). This is with the 07 though, I don't know how an 04 (that doesn't have the VVT)would stack up though. All in all, you bought a nice, clean truck that should have plenty of balls for what you want to do with it. The only time you will regret it is when you are towing with me and I start to walk off on an uphill grade.