Do 13-inch wheels and tires have any value?

The big boys, Pirelli, Michelin, & Goodyear all make a 175/70-13 radial tire. So does Kumho if you want to consider them a major player. The 175/70-13 will give you a slightly smaller rolling diameter than the 6.50-13, but it will give you a slightly larger footprint. In terms of section width, the 175-13 is the closest replacement to the 7.00-13. Beyond a 175mm section width, you're looking at a trailer tire or a racing tire.

The tires you have on the rims are in incredible condition. I'd hate to see them wind up on a discard pile somewhere. All of the first generation compacts, except the Tempest, used 13s. The market for the tires is much larger than just this site.

Because radials are so much better on the street, I agree with another member who suggested that the tires are best suited for someone who has a concours type restoration.

As far as I know, Mopar didn't use US Royal as an OEM supplier. GM did.
(My father and I both had dreadful experience with OEM US Royal tires. To this day, I would not own another one.)