If you go with the 0.64 fifth gear, rear end should be 3.73.
Thats what I have. First gear has tremendous pull. Fourth gear is OK for 55 MPH highway. Fifth gear for 70 MPH or higher - great fuel MPH on long highway drives.
In 5th gear at 100 MPH, I'm only doing 3000 RPM. Just cruisin'
If the car will only be used local and/or trailered, I'd go for the 0.82