I have had an 02 second gen cummins and currently have an 05 3rd gen cummins, If I was looking for another I would look for a 6.7, I have not owned one but they have better pistons than the 04.5-07 5.9 had that were more prone to failure. I have driven a number of 6.7 auto rigs and they have a ton of power compared to my 05 with a smarty Jr.
I would look for which ever body style you prefer be it a 3rd or 4th gen with a 6.7 and all the deletes done already.
I would not be afraid of an auto at all. I have logged many miles of abusive heavy towing with a lot of Dodges and have yet to have a failure, but on my 02 I did replace the stock converter and VB with BD diesel units as I was at 560 hp and 988 tq and power pulled it, sold it with 150K on it and had been at that power level for 100K miles with no issues.
There is a video link of my 02 in action in my signature below.
Last edited by Toon tugr; 12-29-2013 at 11:06 PM.