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

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-