I actually was attempting to find some 15" deer hoof wheels but stumbled on what I got for $80 for the 4 with center caps and lug nuts... it took me several hours to strip then wet sand them to make them look decent (followed by a can of wheel clearcoat).
The problem with 14" wheels is the size you have is as tall as is available, they're relabeled 27" by something or other in some forms like all terrain or winter tires... the sizes available open up a lot in 15" which is why I went with that...
Correcting for the speedo difference tire size didn't make much of a change on mileage at all, with more aggressive winter or AT tires my '97 got 21-22mpg from 27-29" tall (225 70 14 through 235 75 15), once I switched to P tires it migrated to 23-25mpg consistently... I get bored so check most tanks of fuel, in the 60k miles the lowest I've seen is 19mpg towing and screwing around and highest around 25.5... mileage falls if you shift over 4k consistently, increases if you stop at 4k for hard acceleration and normal 3k... best cruising below 3k... a 3L will be similar but with an auto you have less choices...
If you mess with tire sizes too much look into what rear differential gearing you have as taller tires will make it more painful to drive (slow), lower gears (bigger numerical) will make it better, mine already has the lowest factory ratio of 4.10:1 so it's more forgiving than say my '90 was with 3.08 gears... For driveability doing a rear axle swap to change ratios is a good starter project, it's like 10-12 bolts, a brake line and parking brake cable... that was pretty much my first modification on the '90, factory ratio 3.08, got a $15 axle with 3.73's (back in the fordranger.com days, like '02), did a frame swap to 4x4 and got 4.10's then lifted and axle swapped to 5.13's...