Don't get new leaves man until you take a look at the condition of your rear shackle bushings. I bet you $10 they are shot. Stand facing the rear of the vehicle as if you were looking down the axle lengthwise. Rock the truck back and forth and look down, you'll probably see the shackles twisting if the bushings are bad. I pulled mine to add rear extended shackles and the material was 75% gone!

Get some polyurethane ones instead. I would think your shocks are ok unless you are bottoming out or you can bounce the truck by jumping on the back of it and make it bounce a few times.

I installed DOR's rear leaf upgrades and they made a great difference, but bushings are much more important. If they are so far gone, you will even get a clicking noise on sharp turns since the shackle will slide laterally in the frame mount.

If you are up for a real test, remove your rear axle u bolts and jack the truck up by the rear bumper so the axle is completely disconnected. Grab a leaf pack and twist & shake it, if the bushings are bad you can rock the leaf pack laterally and it actuallly rotates a bit around the frame rails about 10-20 degrees -- this is very bad.. when the bushings go bad, they allow for lateral movement of the shackle and allow the shackle to twist as well.