Shocks, the stock ones suck, a lot.

 

5* tune and halo rear shocks.

 

We tow a 6000lb TT. Added 5100s to the rear. That was a huge improvement. This summer I tested out Torque LIft Stabeloads on the rear leaf springs. These also made a big improvement. They take out the space between the leaf springs and the overload leaf springs. When you hitch up your trailer you are using the overloads right away, instead of after almost an inch of sage. Before the Stableloads I found that the rear of the leaf springs would contact the overloads, but the front would not depending on the weight in the truck (passengers). I find with the Stableloads in place the rear of the truck is so much more solid when towing. Completely eliminated the rear end float.

With a heavier trailer and more tongue weight, this may be less of an issue. My tongue weight is usually around 725lb.

If you are interested, they are on clearance from Princess Auto in Canada (I have no affiliation with them) for $216 CDN.