This thing was unbelievably hard to remove, but we were successful. It took several different gear pullers in succession to finally remove it. There was almost no clearance between the pulley and the headstock, and as @wandrson predicted, that booger was really stuck on there. I have subsequently filed a flat where the setscrew intersects the shaft and it goes on and off easily now.
I posted the completed project with the indexing plate / pin / alignment block in the August Show & Tell.