I have a 57 chevy truck and the wheelbase is 1/2in shorter on pass side and I looked and I beam is a 1/2in back on rf is there sometimes two alignment holes on top of I beam and the wrong hole got used or is this normal?
It could have sheered the center pin on the leaf springs from a pot hole hit something similar. Take the weight off the front and loosen the u-bolts to see if the pin is still there. Another possibility is the spring is installed backwards and the center pin just happens to be offset.
That should be a big part of your problem. I'd think reworking both springs at this time would be a good idea.
Sounds like you have a project now. I would think the U bolts would not have to be replaced unless they are bent or the threads are chewed up.