The Ford/Sterling 10.50" axle housing is rated at 9750 lbs in the '99-'04 F250/350SRW/350DRW pickups, per the axle manufacturer.
Stockton Wheel custom made me a pair of 16x8 heavy duty steel wheels for my '92 F350SRW back in late '07, which my truck still has on the rear axle, some 9 years later, with 285/75-16E BFG AT's, rated 3750 each.
These wheels and tires have carried 4000 lbs of utility body and welding equipment in the bed of my F350 from '08-'12, the years I used it as my welding truck, as well as pulling my trailer at the same time. The truck carried my old 8' truck camper (about 2500 lbs) and pulled trailer from '03-'07, with the old 16.5" wheels and 33x12.50 BFG's on it. Now it carries another 8' truck camper on it with the Stockton wheels and 285's.
Never had any problem whatsoever with the Stockton wheels or that model/brand/size tire carrying near the maximum weight for so many years.
The Stocktons are very heavy duty, with solid 3/8" thick flat disc steel centers and thick wall DOT rim shells. I think there still may be my write-up about the wheel/tire upgrade posted in the truck camper help section from several years ago.