There is something seriously wrong with your table because a 1" shackle is not the same strength as a 1 1/2" and they make bigger then 1 1/2".  If I recall correctly a 2" is either a 35 ton or 50 ton.  Thats is working load limit.  Ultimate breaking strength is going to be 3 or 5 times wll, depending on what type of rating you are looking at.