If I remember right, the rims are 6.5" wide. Setback is somewhere around 4.75". Total width of the mounted tire is 9". When I measured the differential I got it was 52" across the backing plates, and 72" total width with the 7.50R16 tires.
Wally/Montana found that some Dodge rims had the correct bolt pattern and center. I'm thinking his were actually made for a trailer, which made hubcaps unusable, my reason for sticking with the GM wheels. The inside of the rim center was the same size.
