Which Shock For My RV


I have a 2005 Ford E450 Super Duty chassis for my Fleetwood Tioga RV which is 32 feet long.  I am not sure of which shock to buy out of the 555010 or 555032?  I haven't towed anything but need a more comfortable drive.  Already looking at the 555031 for the front and I think SC2955 for the steering damper.  Thanks.