1948 GMC 350 (2-ton) with SM-420 4speed and 2-speed rear.
Without knowing the gearing on the 2-speed rear, I'll venture a guess of 45 mph comfortably on a straight/level road, and 55 mph would be an exciting ride.
Do you have good tires.
Do you have good brakes (and a good hydrovac), all properly bled and adjusted?
