I heard that the top speed governor is set by the speed rating of the tires that come on the car from the factory?? If you look at ratings for tires (H,Z,etc.) you'll probably find the speed limited to or below the maximum tire speed rating.
I had a Camaro Z-28 convertable and everyone said it was governed to 102 MPH because it was a ragtop.....Well, it was still pulling like HELL at 135 when I chickened out!!! It came with "Z" rated tires from the factory.
Cobrajack
PS: The Cobra pulls like HELL at the same speed in 4th....They didn't have speed rated tires back then, just big ole BALLS!!!!