I would advise against changing from 3.90 to 3.73 with the .76 overdrive. I am assuming that you are running an inline six.
Your RPM will be too low in 5th gear until you hit 65-70 MPH.
It may sound quieter, but your gas mileage will actually suffer since your engine RPM will be below the optimal power band of this engine between 50-60 MPH. A vacuum gauge will verify this.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission