Coogan---The best way to achieve the look you want is with a z'frame. The front of the frame should have a vertical Z that runs straight up about 1/4" beyond the outside of the firewall, and the rear should have a vertical Z that runs straight up about 1/4" behind the cab.
The 4-link attachments for the rear axle also act as gusset plates for the rear Z, and you can run a suicide front end with a Vega cross steer set-up and 4 bars or hairpin radius rods.
If you don't channel the cab over the frame rails you will always see the frame rails below the underside of the truck, which looks kind of goofy.