yes there were a few options for rear axles
Look here, the axle info is on the Door Tag: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes
The 4 cylinder Rangers can go either way, if original buyer wanted MPG, point of 4 cylinder engine, then he may have opted for a 3.08 or 3.45 ratio, great for highway MPG, but sucks with any weight in the bed.
3.73 was the most popular mid range ratio
4.10 would pull better and not unpopular in the 4 cylinder, when ordered for Fleet work, i.e. delivery or small work trucks, around town MPG was important not long highway trips.
You should also check if you have stock tire size, adding an inch or two to tire diameter lowers the final drive, so a 3.73 might now drive like a 3.45 with a slightly taller tire, speedo would be off as well.
Stock tire size is on the same label, adding taller tires is popular with 4x4s, but there are related effects to doing that.
No, it is not to hard to swap axles or swap the ring and pinion gears, but with a 4x4 you have to do BOTH axles, they need to match.