Welcome to the site;

Are you really gonna run a locker in the front, and a LS in the rear? Seems as though the locker would serve a better purpose in the rear of the vehicle, and might be less of a hassle when you hit the ruts with the wheels spinning at full speed.
That being said, 3.50 gears? What size tires are you running?
That 351M did not make a bunch of power new, matter if fact the factory Hp numbers were a little sad. Helping this thing out is going to make a much greater difference than worrying about shocks.
Get the drivetrain together, keep good tires under it, and make sure you can turn these tires.
You have a few more variables to consider. Being succsesfull in the mud is about having tires that can displace mud, an engine that can turn the tires with adequate wheel speed, and the proper gear selection to help keep the engine in its optimum power range.