Yes, you can definitely replace the one-piece serpentine 5.9 Magnum balancer/pulley combo with the 5.9 Magnum balancer that was two-piece, then run whatever pulley you want.
The aftermarket balancers with changeable weights will work on any year Magnum engine. I am guessing they screwed up the years because it's unclear what year or model or trim line has the two-piece setup. If they sold it to fit later years with a one-piece, everyone would complain that is does not have a pulley.
