Jsut wanted to add that on the rear you will want to pull two from the top and one from the bottom IIRC from the orginal rear pack and put them in the corrisponding places int eh B code pack to get the proper rake and have some flex left in the rear springs. The X is like a 250-350 with 1K payload in the bed. The extra leafs restore the ratios. But double check which leafs to pull its been years since I have done this.
Its fairly easy to figure out if you look at the lengths and where they could fit in the new B code packs. ALso get some more of those spaces the OE have in them and put them between all the packs. They are cheap even from Ford parts dept.