I do not recall Goodyear raised letter Polyglas as OEM for the '68 Firebirds. I started buying them about '70 as replacements to the original Nylon Radials that came on my '68 and I believe one set of redlines which were my first replacemnts in '69. The tires wore out very fast then. I can check my records but I believe I was eating tires at a rate of every 15-20k. It was somewhat confused because I ran snow tires each winter.