Reason I mentioned the sway bar is that it reduces body roll and usually when the body pivots farther from side to side the rearend will step out accordingly, if it rolls less the rearend should not move out as far unless of course I didn't really think that through
what kind of bushings and shackles are you using in the rear leaf spring pockets? I would start by putting in some delalums in the rear along with the heavy duty shackles, and then make sure there are no rubber bushings between the rearend and leafsprings(what you were trying to describe) and then go from there. But if you insist on spending $ and time and addding extra weight go for the watts link.