Wheels on 66 valiant

If you're looking for a nice step up from the stock 13" wheels and tires, I'd suggest something like a 225/60-15. Pretty common size and available in several "Grand Touring All Season" brands and treads. If you are running a fairly stock suspension, it's all the tire you'll need and will have nice highway manners. If you plan on Porsche hunting, you want a more serious performance tire, but you'll also want some serious performance suspension parts.