Arrington bored out the hole where the shackle hanger mounts to the frame. The rivets were knocked out of the factory ones, and they were ditched to make room for a new pair of Off Road Design heavy-duty shackle hangers with more durable urethane bushings and larger hardware. The new ORD shackle hangers bolt up to the frame without too much headache. The biggest issue is probably trying to get the rivets out of the stock ones and off the frame. Usually I would've just used ORD's shackles, but since I somehow left those off the order sheet, Fabworx quickly made up almost identical shackles to hang our springs from.