I had the same problem. Here is what I did to fix. All done at home. Replaced the shocks all the way around, replaced the shackles and pins on the leaf springs. Noted that the clasp that holds th leaves in alignment were shot sot I made and insalled new ones. Took me a weekend and about $200.00 in parts, but he's (trucks are only males) trued-up now with or without the load. Got the shocks from a local auto house, the spring shackles kits from Chevy Duty, and made the clasps out of 3/4" wide flat steel with u-bolt helpers.
