Hmmmm...I'd be willing to bet a lot of 66 273 HP 4 speed cars came from the factory with 7 1/4's. Was the 8 3/4 an option? If so, what was the order code? I always thought ordering the trailer tow package, which included the heavy duty read end, was the only way to get it on a A body car.
My two 66 S's were assembled on 9/22 and 10/14 respectfully....was the factory assembly line really short on 8 3/4's for 3 weeks?