Diff refresh question

Each year I refresh parts of my car. This year is rear end time. Planning to remove and replace bearings and axles. I know something is up in there as it has a bit of a low howl to it since I bought the car. The weather is closer to favorable conditions for working on.
Now my question is at present it has 3.73 gear which is fun but I spend time touring and not racing. I was thinking of just rebuilding with 3.55. Still have fun time but maybe a little more distance on a tank of gas. Or just pick up a complete diff and build it with 3.55's and park the 3.73 diff on the shelf for a later date? Or just rebuild the 3.73's and tour on? I have all the parts except gears ready to go.
Any thoughts anyone?

If you are buying gears, only buy Ford racing. Best chance for quiet gears.