i'd agree with adam.
I wouldnt even bother with a ranger engine, it will get the same MPG as any v8 you put in, but have less power, my cousins 03' 4.0 v6 ranger eats gas as much as my 3.4 4runner... which is no prize hog to begin with. bout the same 0-60 too.. SLOW...
in a little 2wd reg cab they are quick, in a x-cab or SUV.. not a chance, not worth swapping.
If you want a ford, do the 302... it'll get the same mpg as a 3.0 or a 4.0 but with way more torque... you could even run 4.10's with 33's or 35's to drop your highway RPM's to get even better mileage...