I had a neighbor who ordered a new 1968 Mustang with Metric radial tires. The tires on his car were supplied by Michelin. Within 5000 miles all the tires were split, the dealer installed new ones under warranty. Those tires were bad before the car had even reached 10K miles, the owner demanded and got a new set of bias ply tires installed.
I suspect the T-Bird in question has optional Michelin or other brand radial tires. I think they were a big problem back then!