Axle offset

[Gizmo 007]

Well, it's time to put "Blue Thunder" to work. This weekend I pulled the bed off of my 3500 to put in a custom homebuilt gooseneck hitch (35,000 pound rating. It's huge). Anyway, I got to measuring out the frame rails and noticed something I didn't like. The rear axle is offset to the driver's side almost 3 inches. I can't see any reason for it to be out that far.

Anyone else have this problem? You may want to check. I measured from the top-inside of the tread to the frame rail. If anyone has any suggestions on how to straighten it, I'd appreciate it. 35 grand for a truck and you get this Sheesh!