I would suggest a one year old off rental/lease 3500 Chevy/GMC with the 6.0L. That is what I just purchased. 21,500 for 2013 with 14K miles. We went with the shorter wheelbase for daily driving and we are only a family of 5. I haven't towed the TT yet but pulled the boat last week (24' pontoon) and was completely impressed by it's towing capability. Love the 6 speed transmission.
Only problem with the E350 in the off rental plan is that they will not have the V10 engine. I am also not a fan of the large rear overhang on the extended chassis. The GM twins change the wheelbase for the extended chassis.
