There are two eccentric (off-set) bolts and four regular bolts holding the front bumper irons to the front frame cross member on all '57 Olds, and maybe some other years. These off-set bolts turn in the holes in the frame cross member to adjust the height of the bumper. Mine are in rough shape, and I would like to buy a good pair of these off-set bolts if there are any out there for sale.
Thanks, Bill

 

Try fusick automotive

 

Fusick won't have them, but I do. In fact, I have the complete front bolt set. PM me for pics if your still interested