255/60/15 tire availability

...but by the numbers, as stated in the thread above, Both the the Master Craft and the Cooper are better tires for a lower cost. Cooper has at least as good a brand reputation as Goodrich (again, actually made by Coker), and I'd wager so does Hankook. Hankook is taping the specialized labor force in Akron, OH, as the other American MFGs are laying them off. That's smart business.

My 255's went right on to the 6.5 rims with my ancient Atlas changer. No stretching or undo resistance. They look like they were made for them. No bulging sidewalls or crowned tread surface.

If you want to go to the track, I think an affordable drag radial on a spare set of rims is probably the path of least resistance. Maybe even a sticky street/drag tire (like the MT), so you can drive to the track and change them out at home.