There were two versions of the 3/4 ton diesels in a few years. Some were HD some standard. One big difference is in the front ball joints. These are expensive to replace.

I would jack the front wheels up and check the front ball joints. It seems to me like they shipped heavy diesel engines on lighter gas front ends for a couple years. Maybe ask to take it to a mechanic who can check the ball joints for you before you finalize the deal.

That is about the only issue I can think of with these - depends on how its been treated also. 66k is about when the ball joints on the lighter frames tended go.

Good luck.

Jim at Dawn