My '96 3500 2WD doesn't have spacers on the front, it just has these REALLY extended hubs, and it also looked like the brake rotors were part of the hub. I know that sounds crazy, but when I replaced the front pads I sure couldn't see that the rotors were a separate part. The extended part with the wheel bolts was definitely part of the hub. Can someone tell me, is it only the 4x4's that have hub extensions?
My suggestion would be to just run 4 of the dually wheels, using only one on each side in the back - along with a single wheel bed. This will result in the tires running in the same locations as if you had a 2500 in the first place. It may look a little strange, but - so what?