Fair guess it does, Birge. My '51 was near topped out at 45, and 50 was not sustainable with the original 5.14 ratio. In those days I had 7.50 17" tires, and a 35 - 40 mph cruise was where the truck was happiest. I was always in top gear. Now I have 235/80R16's and a 4.11 diff, and life is about 30 times easier on the road. I still have the SM420 backing up the old 216 and I might never get an overdrive, unless I get to long-distance driving the auld girl when I retire. She'll do a steady 60 mph without difficulty if I want her to, and after 30 years of driving transports for money, that is plenty fast enough for me.
