I have an 03 CTD 3500 quad cab 4wd 6 spd. with 4:10 axle. I've been towing my 35ft. Travel Supreme 3 axle fifth wheel which weighs about 15,500# wet. Haven't been very far with it, but we're thinking about going west this summer,(about 4500 miles round trip). I'm concerned about the SRW setup with that load (lose a rear tire at highway speed, and, BUMMER!). I have about 2700# hitch weight. I'm thinking about trading for a new '05 dually with automatic. I measured the height of my bed at 56", and the dually 4wd is 59". With my trailer sitting level, the bottom of the overhang is 63". Is that enough clearance? Also, is the 48re transmission up to the task with a 4:10 axle? I can buy a 2wd dually, but I really like the peace of mind that comes with the 4wd!