Sounds simple enough, new truck, old cab...
Why don't you look at some of the medium duty fords, they have the 5.9 Cummins in them stock.
What size truck do you want, 1 ton, 1.5, 2??
If you go with anything over a 1 ton it may be easier or better to use the original frame and add engine, trans, and axles.
Grigg
