They work on 1 tons too. The 4x4 guys I have seen with those wheels use a hole saw the same size as the emblem in the middle of the cap and they work perfectly.
I think they are 6.5" wide. I have the steel version of those wheels and they are 6.5" wide. look on jeffs pic... see where each lug nut is, theres a little hump on the outer edge of it? well the steel wheel caps dont have that, thats how you can tell them apart.
See on mine the caps are smooth around the outer edge.
To DYNO: if you do buy center caps seperately, they have to be the caps for aluminum wheels, the ones for steel wheels look identical, but they are bigger around where the cap meets the wheel and won't fit on aluminum wheels.