Looks odd with those skinny whitewalls. This was a 1967 Goodyear tire promotion special "Super Snake." Most valuable Mustang ever, as it sold for USD 2.2 million in 2019. From Road and Track: "...one-off GT500 was built as part of a collaboration with Goodyear to help them promote a new line of economy "Thunderbolt" tires. Shelby's goal was to build a car that could outperform anything else while wearing these tires, so he had a GT500 built with a 427 cubic-inch racing V8 to the same specifications as the GT40 MkII raced at Le Mans, along with an upgraded transmission and rear end. He then had the car driven for 500 miles at an average speed of 142 mph as a test to see if the tires would hold up. The test was a complete success, with the Thunderbolt tires retaining 97 percent of their original tread, and the car topping speeds of 170 MPH.