4.56 gears, a locker a 33s is going to put a lot of strain on the axle, might as well start with an 8.8, even if you can only find a 28 spline from a Ranger. At least it will be bolt-in.
The 31 spline from an Explorer or Sport Trac will be a little stronger, provide more options for lockers, and come with disc brakes after 1995, but will require a little bit of welding for spring perches and shock mounts. You can also get an Aussie locker for the 31 spline 8.8 which is normally a bit cheaper than powertrax/lock-right.
Personally, I just wouldn't want to spend the money for new gears, install kit, a new locker, and labor for a 7.5 axle.
2006 F150 FX4 Super Crew - Bilstien 5100s leveled 2", 35" KM2s, 4.56 gears, Detroit locker, Eaton E-Locker, Traction Bars, AEM intake, Xcal 2
2010 VW Golf TDI 6MT