Chevy called the optional rear ratio 3.07 in 1963. That will probably be needed to wind up the 140HP to 70MPH without stressing motor or mileage if most of your usage is highway. The 3.73 was the std ratio. Sounds like you have a set of parts to do the swap. Good luck. Let us know what kind of effect it makes on both ends.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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