You did not mention the year of the truck. My '37 has the same type of hangers and bolts. I have the springs off now so I was just under the truck. The hanger is threaded, no replacement parts on the hanger itself. The bushing is pressed into the leaf spring. I don't really understand the reason behind the threaded hanger, maybe to keep the bolt from spinning? The outer nut and washer just lock the bolt in place.
I would hunt for the correct bolt and nut, drilling would be a last resort.
Joe
