The next highest ratio would be 3.08. Is it your opinions that it would turn it in to a zero torque truck in 5th?
Yes. We had a '90 2.3 5-spd with 3.08 gears and it was the slowest thing I have ever driven.. could not maintain hwy speed into a headwind and OD was nearly useless on the highway. The thing spent most of it's life floored but it still returned a solid 25mpg everywhere all the time.
Incidentally our two 3.0L 5-speed trucks also return much the same gas milage but are much nicer to drive.
My '91 Ranger with 2.3 Lima engine, 5 speed w/OD and 3.08 gears was fine. True on a long moderately incline, I had to drop into 4th gear, otherwise if was more than adequately powered for 70 mph running, even pulling a trailer.
I had a best of 35 MPG (CDN gallons) in a 93 2.3 5-speed. I don't recall the axle ratio, but I am guessing it was a 3.08 from the description others give. 5th gear was not usable going up any grade, including at 60 MPH. I remember one time on a 70 MPH highway not being able to use 5th on flat ground due a strong headwind!
I've got an old (91) 2.3, 5spd Ranger Supercab 2wd with, I think, 3.08 gears. The truck was priced right (free) and the powertrain moves it along fine. I have to drop out of overdrive on some long hills, but that's a small price to pay for 24 mpg local and 28 mpg highway.