Boomerang shackles are designed to clear the rear frame crossmember in a YJ when the spring fully compresses. Many YJ's crossmembers are dented where the stock shackle hits it under compression.
Lift shackles help clear spring eyes that have the military wrap, but do nothing to help clear the rear crossmember.
Revolvers help flex by adding droop to the suspension, as does the ZigZag.
Never pull a stuck vehicle by the shackle or any suspension part, and never weld on a tow hook.