Is this for the 91 Ranger in your profile? If so, the Explorer axle and the mustang axles will be a good bit wider than the stock axle, which may limit the amount of tire you can run without sticking out past the body.
The mustang axle also has the carrier located in the center, while the Explorer and Ranger axles have an offset carrier so that the driveshaft doesn't rub the fuel tank, so you'd have to figure out a way around that.
There are brackets available that will let you bolt Mustang brakes onto an Explorer rear axle, or the ranger 7.5 or 8.8.
If you want to run a decently wide rear tire, and don't want it sticking out past the bedside, you'll have to narrow the mustang or Explorer rear axles, but the explorer axle would be 31 spline, trac-loc, disc brake already, and would have the dif offset like your stock rear end. The only way Id use the Mustang axle is if you're going to use a 4 link, and move the fuel tank location. Otherwise, the Explorer or Ranger 8.8 is probably the easiest option.