is it posible to change out the diff housing with gears and all without having to mess with realigning the gears? it in a 93 f 150 4x4 with 373s and i found a late 80s or earlier 90s f 150 for cheap and it has 410 gears and lower miles

 

depends on the rear end you have. pretty sure the 9 inch is "hot-swappable" like you are saying, any other rear end you have to pull the diff apart to change gears.