If MPG is the only concern then yes, EFI, but V8 swap is usually more about power than strictly MPG.
And driving a pickup truck in general means MPG is not a major concern, lol.
Yes, carb setup is basically 1 wire for spark, 1 wire for oil pressure and 1 wire for coolant temp, engine wiring is done, lol.
Carb and HEI distributor setup with 302/5.0l can get decent MPG in a Ranger, look up the old, pre-1980, F-150 302/5.0l numbers for MPG, Ranger is a little lighter and Factory specs for MPG are a little higher(optimistic), lol, so they should be about right on for what to expect, mid-teens.
Manual trans with OD would give best numbers but AOD(no computer needed) should be OK to use, locking torque converter will give best MPG, non-locking best power.
Definitely use an electric cooling fan on rad, bumps up MPG and power, not much but not 0 either.
2-barrel carb with manual choke would give best MPG, although new 4-barrels are worth a look, better fuel dispersion.
Carbs use 6-9psi fuel pressure, if you have an 1986-1997 Ranger you will have 35psi, so you will need a fuel pressure regulator to drop the pressure down, or switch to mechanical pump and remove in tank pump or replace it with lift pump
Vacuum gauge on dash lets YOU see when you are getting best MPG, helps to keep your foot off the gas pedal
Driving habits account for 3-5MPG