Nice man, I wish I had the balls to do something like that. LOL  So how did you do the watts-link?  I've seen kits where they bolt on to the differential cover plate, but have never seen one like that before.  Gives me ideas................
The Watts-link is the way to go because of what TS6034 mentioned.  A panhard bar would work but you have to set it up exactly right.  The bar allows the rear end to shift slightly during compression/rebound.  A spring suspension may not notice this at all, depending on how close to the wheelwells you are running.  With a bagged truck, the suspension can have a travel of 6+" and that much of a change would be noticable w/o the watt-link.  
James