I test drove a 6. 7 auto and it does drive and shift nice. The 5. 9 auto just didn't feel as nice on the test drive. The sales man filled my wife's head full of crap about how the ONLY difference in the 5. 9 and the 6. 7 was the bore and stroke (no other differences). It got to the point where I told the sales guy “if you don't find the 5. 9 auto that meets my needs I will go to another dealer to find one”. He quickly got the picture and started working in the direction I wanted him to. My next task was to reprogram the wife back to the condition that I had her programmed before visiting the dealer (only a 5. 9, or we wait a few years till the bugs are worked out). Two days later I drove off with a 2007 5. 9 auto. One week later I dropped it off at Rips for the long overdue transmission work. After a billet input, triple lock converter, valve body, etc the truck was transformed into a dream machine. Coupled with a Smarty the truck feels like it shed about 5,000 lbs and performs like our beloved E55. My advice to friends and family is “get the 5. 9 now while supplies last”. I believe the 6. 7 is a great truck, but I wonder if the potential to modify will ever catch up with the pre 2007 emission vehicles. I am very happy with my 5. 9 auto with Rips transmission mods.