I'm changing my lottery win choice: I just checked the Kelsey Tire site and they now offer the Goodyear Steelguard GR70x15 which according to Goodyear came out in late 1972 for 1973 cars. That might be the way to go for the future, for anyone else cursed with the Firestone 500 GR70x15 under the radial tire option. They offer them in both RWL and white stripe.
https://corporate.goodyear.com/en-US/about/history.html
https://www.youtube.com/watch?v=oLK_nZeD834
http://www.kelseytire.com/pages/preformancetires4.html (4th tire from the left)