Confused

[dwelch44805]

I am looking to buy a used (2000/2005) 6.6 Duramax Dually 4x4 to tow a 5th wheel.
Are there years I should avoid?
Are there years I should focus my search on?
What milage should I run away from?
I was a diesel mechanic for 15 years until about 1990.
I also manage mobile tool distributors that have C5500 with the Duramax and I really like the way they perform.
I just don't know about the older units and don't want to buy a headache.
Don't tell my wife, she works at a Ford Dealer.
Any and All advice will be greatly appreciated.
Thanks

[THEFERMANATOR]

I know you said 05-, but it's hard to beat the 06 and 07 classic. By 06 GM had most all of the bugs worked out, and there isn't a DPF on them either. Couple that with the updated 6 speed ALLISON and you have a potent combo. 01-04 LB7's have injector issues, but the latest injectors seem to be proving themselves much better than the ones before mid year 2008 did. And the 04.5-05's had some other issues with them that dealt largely with overheating on some units. 06-07 classic though have some serious HP to start with, and didn't suffer from the injector problems or overheating of previous generations.