Best upgrade for ride while towing?

[penra]

My truck pulls my rig beautifully but not perfectly and I'm considering a couple of options for upgrading. When driving on some California highways I get a bouncing going. It's minor but annoying. If I hit some rough patches (like the transition from bridge to highway) it can give us some serious jerking.
I'm thinking of an air ride pin box or air bags for the truck. I'd love to hear from this forum about which might have the best result or even if there is another avenue to consider?

Specific pin box experience would be helpful since there are several options.
thanks!