17X8" can be a perfect fit. If you run 255/50/17 tires, the circumference if nearly identical to 255/60/15s or 225/70/15s, so you shouldn't throw off the speedometer. Are you going with the 4.5" offset beacause that's the only size offered in the wheel that you're looking at? That's not a huge...
Theory has it that an 8" wheel is actually 9" wide. The 8" measurement is taken on the inside of the wheel where the tire bead sits. The wider 9" measurement would be the actual width of the wheel on the outside lip or flange. I've never seen a 1/2" wide "lip", but that's the theory. :quote...