the shock has nothing to do with sqauting... the springs are what support the truck, shocks only dampen the the up and down travel. Unless you run air shocks. If your going to pull you only need to have 1" of suspension travel so run a longer bumpstop and your truck will only squat 1" and the shocks wont matter one way or another on the rear, as for the front thats not really going to matter that much either but you will need a shock that is in good working order...
I personly like hydro skocks myself.
just my$.02