Tire size question

[1984 t type]

About to pick up a stock 84 Jimmy, suspension seems to be in real good shape and the springs do not appear to be sagging. Currently it has the stock rally wheels with 31x10.5r15 tires on it, it needs new tires and i am purchasing it out of town while im here on business and planning on ordering new wheels and tires and having them delivered to my hotel and driving it home. What im wanting to do is order a set of 18x8.5 -6mm rally wheels and mount some 285/60/18 Atturo Trail Blade X/T tires on it, they measure out at 31.5x11.5x18 so a half inch higher and 1 inch wider. Has anyone ran this size tire or think i will have any issues with them on a good stock suspension truck ?

Thanks