Good God how the prices of speedo gears have jumped up in price. I bought several from the Jeep dealer when they were still around at a cost of $5.00 ea and I thought that was a lot. It's no wonder I hold on to them like gold, I don't know why, but I do.
For good mileage around town and decent highway acceleration, I would not go below 3.73 gears for the T5 and 32" or 33" tires. I have 4.10 gears with 32" tires and the T5 and love it. It's a great combo driving around my area with many hills and winding roads.
And yes, as others have said, a T5 trans with large diameter tires and 2.73 gears will destroy the trans in no time. Too much stress trying to turn the added weight and diameter of large tires without the proper gears. It's the reason the T4 and T5 get such a bad wrap as being a crappy transmission.
1984 CJ-7 Renegade