I have been working on wheel mounting lately. The body kit mfg says you need to use a 2 inch wider wheel and buy expensive custom made 12 inch wheels for the rear and 10 inch for the front. I plan to skimp by using off the shelf existing 10 inch wide wheels. I am using a 10 inch rear wheel for a 99-04 Mustang which is offset outward 1 inch. Then I replaced the stock 2 inch wheel studs with 3 inch drag race type studs and a 1 inch spacer. There is my 2 inches, and the wheel sits flush with the outer lip of the wide body quarter panel.
Still working on the front wheels but I believe I will be using longer studs, a 1/2 inch spacer and the same 10 inch rear wheel.