Not to be redundant but I can confirm those who said the rear ratio is too high for an OD with a stock 235-6 cylinder. It is straining the engine to pull the car at 65 and it would even be worse at 55MPH. Get some 4:11 gears in your booty. And get a tach and vacuum guage to prove the point.

1953 Chevy 5-window 3100
In the Stovebolt Gallery
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Dave
Engine & Driveline Moderator

If you can't make seventy by an easy road, don't go. ~~ Mark Twain