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.
“the faster one went the smoother the handling.”
The same with my ‘91 Lexus. At about 90, it just settled down and got better. I chickened out at about 140 though.