31's, 2.3 and 4.56 bring the truck back to stock power.had this combo in my 87.pulled a constant 20mpg no matter how I drove it.top speed will be right at 100mph, and you be at about 3 grand at 70,about 300 rpm over stock, but makes up for the weight and resitance of the larger tires.
If you go 33's you would be better off with 4.88's for daily driver, 5:13's if a play toy....poor little 2.3 just dont have much power, they are in general like a timex, they take a licking and keep on ticking. but just dont have much power...and its not so mcuh getting the tires moving, its keeping them moving.
the 91 I have now with the 4.0L also has 4.56's but its on 33's. I find it perfect over all.had 35's on it for awhile and I found it a little lazy...not bad really, but lazy.This truck pulls a avg of 17mpg even with my lead foot.Yes my tach pretty much sits at 3 grand on the freeway,but im in a truck, so I dont need to keep up with the mustangs...and Im not driving a escape so the loss of a mile or so per gallon did not bother me to have the extra over all grunt.