With the post 98.5 Dodge Diesel's (24 Valve Cummins) I've heard that its really important to have a fuel pressure guage. Take that for what its worth.
If it were me I would buy a pre 98.5 (12 Valve Cummins) with the lowest possible miles you could find. You can do more to a 12 Valve (performance wise) than a 24 Valve, and still pull down better mileage loaded and unloaded than a 24 Valve.
Check these out...... www.TurboDieselRegistry.com
On TDR though you have order a subscription to become a active member, but you can always just glance through.
Diesel Central is free.