You should be fine.
I have eagle alloys on my FX4.
15X8 with 3.25" back space.
I have the stock 31X10.5's on there.
They don't stick out. They are almost even with the fender flares. They have the perfect look IMHO.
they rubbed slightly on the stock mud flaps when I put them on at full turn, but; a slight bend with my hand of the little bracket on the mud flap cured that.
They don't rub anywhere else with the 31's.
You'll be happy!!