My 5.4 '150 with really high gearing (3.31's) and oversize tires (32's) gets the same mpg my former college roomate got with his stock '00 Ranger with the 4.0 (16mpg) On stock rubber my '150 was bumping 20mpg, seats 6, tows 7k lbs... I looked at getting a new Ranger but it kept coming up short... especially since I was keeping the '85. A nicely equipt 3yo '150 with 25k miles was actually a little cheaper than a comparable new Ranger... so I went that route. 6 years later I haven't regretted it.
Basically it came down to even a SOHC 4.0 Ranger couldn't do much more than my old 2.8 truck, it would still be limited to hauling brush and lawn mowers and that was about it. Came down to I might as well buy a car to get better milage since the '85 was staying. Or I could get a fullsize with similar or better milage and quit borrowing trucks (which I hate doing) to tow my tractor.