Tom, GM's with the new Duramax engine have been out for at least a couple of years now so there's a chance there may be one out there with your name on it. From what I hear the Duramax is a good engine and I think they are available with an Allison automatic transmission which is a company known for building HD transmissions.
The 6.5/6.2 diesels have their faults but I've heard that the IP's are easy to work on or at least cheap to replace should you need to.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012