1954 3106 Suburban:
261 with 3.55 rear end, and 31.5" rolling-diameter tires.
My MPG at constant speed highway driving (approx. 60-62 mph) is approx, 18 mpg - at approx. 2300 RPM
I see the gas mileage decrease significantly as I increase speed (getting around 12 mpg at approx. 66-68 mph, 2600 rpm).
I will not post how fast I have driven the truck, but it starts getting "squirrely" (wandering) at around 75 mph.
