Speedo is corrected, yes (well, about 2 MPH fast at 65 still, biggest gear available)
The couple times I broke 24 MPG could very well be due to tailwinds, once was on the I-10 going east out here in San Bernardino Co. Ca. It consistently blows enough there that they got a huge windmill farm out there.
But I also tend to drive a bit on the slow side while cruising (55-60 MPH). I know that much faster than this, the MPG tanks out big-time (probably less than 19 if I keep a sustained 75 MPH).
There are 7.5" 5.13s available, but I would still swap to the 8.8 for the bigger pinion gear at that ratio. The 8.8 from a 4.0L Ranger is a straight bolt-in swap.
edit:
with 30s, 4.10s might bring some improvement, although MPG seems to be a mysteriously variable thing on 2.9s. Why this is I don't know, but it seems I was lucky to get one of the better ones (it did about 26 MPG when I had the dinky P205 donuts and 3.73 gears)