Well, your engine isn't running all that efficiently (rpms are below the power band) and odds are you could boost its mpg a tad by regearing it to the correct ratio. But how long would it take to recoupe the approx. $1200 cost to regear by a couple mpg improvement?
That said, I would regear anyway. With your 3-speed automatic and 33" tires, 4.10 would be a very good all-around ratio.