245s are pretty much flush on a 9" rim, 215s will look a little stretched on a 8" rim but it will work. I think they'll be too narrow just overall but they'd make a great snow tire.
I always see ppl putting too big of tires on their rims like 275s on a 8" or even a 9" is too big. You want the straightest sidewall possible on a street radial to elminate sidewall flex. I'd rather have a little stretch than a tire bulging over the rim. That's what I HATE about my front tires. The PO put 265s on a 9" rim and they bulge out a bit and it makes me twitch a little when I look at it. Should have been a 245 or 255 on that rim goddamit...
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.