The 20" wheels on my 4400 have the outside ring. The bolt hole pattern is 7.250" and the center hole is 4.750". I have found some 19.5" 10 lug one piece wheels that the bolt pattern is 7.250" but the center hole is 5.250. These came off an old GM motor home. I was told that some wheels off of some 3500 Heavy Duty Chevys will work also.
If you find some be sure to check and make sure they will fit over the rear hub. The back of my 4400 has 16" hubs and not all of the wheels I found will fit over it.
I haven't put much weight on the truck yet but think that before I do I will make a spacer to fill in the space in the difference between the 4.750" hole and the 5.250".
