Saginaw boxes are basically a bolt in setup. I have one from a FSJ sitting and ready to go in.
As for the pitman arm, you will need the drop pitman arm needed for lifted FSJs as the stock M715 pitman arm is pretty low and stock FSJ arms are almost straight out (better design, but doesn't fit our geometry.
One more thing is that you will DEFINITELY want a some kind of bracing for your steering gear because of the added stress.