Finding a used set of optimal springs may prove difficult and are often removed because their worn out, but you may not know until you install them. My old ones were formed around a 4in lift block and rather flat. I wanted to remove the block, so had a set made to lift the rear the 4inches, and with multiple leaves to be more progressive. The ride is way better and there's much less axle wrap. I have no idea what your set up is, but it might be worth considering just having some new ones made. Deaver's are really nice, but very expensive and have a long wait time to boot. There are other manufacturers out there that are less expensive with a quicker turn around.
Agile Ride improvement package