Here are a couple of pics of the rear shocks/springs. Let me know if you see anything blatenly obvious.
Pic 1 Pic 2 Tires are radial, by the way.
Steve,other than the lower shock bushes being at a slightly strange angle,to me the bolt should pass through at right angles to the shock body,everything else looks to be OK.
I don't think the angle would cause any more problems other than the lifespan of the lower shock bush.
Usually excessive bounce is down to 'dead' shocks,like JoeH mentions I would remove a shock and check how much resistance there is,as you've added considerably more weight to the rear of the truck,a full gas tank is pretty dang heavy!
