I dont think you will have much problem with width, see the pic I posted, they only use a slight flare. Probably more for good looks than actual requirement. The standard 6 inch rim will accommodate a 225/70/16 tyre no problem (they use a 205R16 as standard).
A 235/70/16 mite leave a bit of mud splatter on the guard, but not worth worrying about.
Plenty of rodeo's run around on 10R15's tyres. I run 9.5R15's, which I reckon are as wide, or wider than the rubber in your pics (the rim does have a bigger offset tho).
If the alloy doesnt have a washer receptacle, then those nuts look ok.