[Coupeguy2001]

Steve, Great looking truck!
Are you running traction bars? Sometimes ones that don't slide or slap cause the spring to work in rebound only and eventually the bars break.
Another thing, are you sure the driveshaft isn't too long now? If the driveshaft used to slope down to the axle, and is now semi level, you could be bottoming out the shaft.
Another thing, did you install shorter shocks? I know the original shocks have a lot of travel, but it's worth a look.

Also, from what you described, the springs aren't flexing. Could there be something wrong with the shackles not working and are bound up?
Sometimes, the threads get water in the grease, and rust in place, not allowing the springs to get longer when compressed.