18" or even 19" wheels with a (typical) 26" tire are going to "ride" just fine. That's what comes on most mid/full size cars in 2020. They'll work great on a '60s car too. The problems start with 20" and bigger wheels. There is almost no sidewall, and going to a larger diameter tire will not work (i.e. fit) in most cases. Plus, they start to look very cartoonish at that point. And that's really where the "looks" come into play. But, everyone has their own opinion.
