Run 8" wheels for 10.50 wide tires.
Run 10" wheels for 12.50 wide tires.
Or run 8" wheels for 12.50 wide tires and you'll have some poor man's bead locks.
If you run the 10.50 tire on a 10" wheel, the edge of the rim might stick out past the tire, and be prone to dents, dings, knocking weights off, etc. Probably not a problem with steel wheels, but you could ruin an aluminum wheel just by "mall crawling".