Cobra R wheel question..

Pretty sure tire sizes for the 10.5's would be 285/40, 295/40, or 315/35.
I got 285's on 9 inch but it was tight. As for your original Q......if you plan on running a closer to stock tire size on the front meaning 245/45 then stay with the 8's. If you step up to a 275/40 for the front, run the 9's. It all depends on how you want the tires to look. You want the sidewall bulge to be the same from front to back. It doesn't look good IMO if you have a tire on the front that is blown out on a rim to wide for the tire, then pinch a tire on to a wheel that is too narrow. That is part of the reason for running differant width wheels aside from proper tire wear and safety, but who cares about that. Keep in mind also, if you run directional tread tires and differant sizes from the front to the rear, you can't rotate unless you have the tires de-mounted from the wheels....big pain.