I seem to remember the Hawk doing 149mph, on the salt flats.
Great memory! And that speed would have been possible for a weekend amateur who drove the car to the salt flats. Would not be surprised to hear of routine 150+ mph with a professional tune and competition tires.
The 140 mph designation was, of course, somewhere in the 4-4:30 area of the 1957's gauge. There were a few times during the very early hours of the morning on recently constructed, long and straight California freeways out in the middle of nowhere when I was able to get the needle vertical (yes, I was alone). Never had the speedo calibrated but calculated that even with error I was moving right along.
Pretty sure the magic was in the supercharger plus the fact that the faster one went the smoother the handling.