if you wanna upgrade up to 33X12.50 then the 15X10 wheels would be ok, but until you buy the 12.50 wide tires you will bang you rims up, and pop the beads on your 31's. i run 33X12.50 on my 77 with 8 inch steel wheels. i have no problem, but i have never ran down the highway with that truck. my buddy that owned those tires before me had then on his f150 with 8 inch wheels and he drove the piss out of that truck. highway and offroad.
1977 Cherokee ChiefEdelbrock 1406, 33X12.50, front 1.5 inch shackle lift. AMC 360, th400 Quadra-Trac
2002 wrangler, stock 4.0, auto, 33X12.50 maxis buckshot, AEV Highline Body kit, Ford 9 inch rear end.
Soon to come mods: 4" full traction lift, 4.56 gears, 35X10.50R15 boggers, 35X12.50 cooper st tires, spooled rear end, and much more.