J,
It sounds as if you have approached the resolution pragmatically.
The crossframes used to be made up on a jig and that should have prevented the variance in the camber; however handmade and blacksmiths' techniques prevail!
The camber variance could come from a pair of poorly made and/or mismatched bottom camber plates (the plate that attaches the kingpin to the crossframe. It is remotely possible that these are mismatched. A visual check with a torch and ruler might reveal something or confirm that it's not the source of your problem.
