@dbrock
What mohemipar & mtnrider said, air down your tires a bit and get an alignment. Try airing down to 55/50 PSI (front/rear) or 50/50. That should help a lot. I've even see recommendations from other members as low as 40 psi for the rear.
I usually run 50/50, but it's travel trailer season. So running 55/55 and I can tell the difference. I leave the generator and other camping stuff locked under the tonneau. If I get a chance or a wild hair, I just want to be able to connect the trailer and go. Padre Island National Seashores has a fresh water fill and dump station on site. And yes, 55 psi works great. My 37s are only rated for 65 psi. All loaded up, when my tires heat up, the rear tires hit about 60 - 62 psi while towing.
IIRC, the Bilstein kit is just the front, right? So all you got for the rear was the shocks? The rear springs are the ones that are really stiff. The fronts have the weight of the engine to calm them down. The rears don't soak up bumps until you get a good amount of weight in the bed. You can try putting 400 lbs of sandbags in the bed to see if it helps. I know when my bed is loaded with a yard of topsoil it REALLY improves the ride.