Swapping out the differential has some problems, but is a possibility. Biggest problem is that the newer differentials are wider. What you need to do is measure the distance between the brake drum faces. Also measure the distance between the fender wells, and the setback on your wheels. (Lay a straightedge across the back edge of the wheel and get the distance to the face that mates to the drum.)
Then you're off to the junkyard. The best swap is to a newer 14 bolt full floater. Just about any yard has them with 3.73 gears. Measure the differentials like you on your truck. Most are at least 3.5" wider, which will mean you need to find a pair of wheels with one or two inches more setback. Be sure what you choose will fit in your fender wells.
Next you will have to remove the spring and shock mounts, and weld either your mounts, or mounts from a donor on your newer housing.
All things considered, the pumpkin swap is far easier, but you're stuck with 4.10 gears, which are better than 4.57s.
