Talked with one of my "stance" gurus. 195/40/17 would be safe on both those wheels and give you a good bit of stretch, the 8.5 wheel will be slightly more aggressive. Check out tyrestretch.com to give you an idea of how some tires sizes look on different wheel size combinations
As for how much of a spacer, that's going to depend on how aggressive you want to go. Best bet is to put them on, and eyeball about how far out you want the wheel pushed out and go from there.