Front crossmembers on 55-57 Chevy car frames were notorious for sagging in the middle, which produced a negative camber situation which could not be corrected by shims. We would set up an I beam, jack and chain fixture and push the center of the crossmember back up into its original shape so an alignment could be done properly.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!