CHANGE IT TO METRIC YFI!!!
WHY do you want 8" wide rims??? You're just going to: limit your tyre choice, reduce the number of companies willing to insure you, make your car dangerous to drive in wet weather because it will aquaplane, and cause excessive tramtracking on uneven roads...
But ofcourse there's no way of stopping you. The best way for you to learn a lesson in life is go right ahead and do it wrong so you know better for next time. I am testimony to that sentiment...
Gav.