I have a 2005 GMC 2500 duramax and I tow a new 303RLS reflection (just got it) You can see the pic in my profile (excuse the salt on the truck) and it is with my winter tires 245/16's on the truck....
I installed Bilsteins on my last MH (E450) at 2,000 miles and never had a better or more controlled ride.
For my current '12 F350, I'm replacing the junk OEM shocks at 25,000 miles (way past due) with the Bilstein 5100 shocks and a 5100 series steering damper--best price I found was Amazon with free shipping.