Probably the main reason you ride rides bad offroad is because you only have 3" of up travel. If you want to go fast you need at least 6" of up and a standard 5100 bilstien will get the job done. So you may want to consider adding a leaf are re-arching your springs so they don't sit so flat at ride hight and remounting your shocks so they have more up travel. In addition, post a picture up of your shackle angle at ride hight. We can tell ya if it's at the correct angle or not.
FOA shocks are great shocks for the money. I'm sure they'll hold up more than good enough for what you're going to be doing.
