The KB7 is a rather large truck and does not qualify as a pickup truck. If this were my project, I would be looking for a Ram 4500 frame. Most if not all of the Ram 4500 trucks came with Cummins power. The back 2/3 of the frame, behind the cab, was straight and did not have the hump over the rear axle.
http://hoytedodgeramchryslerjeep.com/ra ... cab-truck/ Finding one of these frames may not be as easy as locating a Ram 2500 or 3500 frame. the straight frame is the better way to go and may be worth the extra search time. If you find a frame with some damage, a local frame shop may be able to recertify the frame after a straightening.
There are auto wrecker networks that connect with each other on the internet. I have used the online network to find Dana 44 axles, an NVG 4500 transmission and an NVG241dld transfercase. If you cannot make the online connection at your PC, any one of the members will be able to help you.
Having the 4X4 and engine mounts is a great advantage and may be worth the while if fabrication is not your strong suit. Some fabrication and welding may be required. A buzz-box HF welder is not good enough.
If you think you may run out of room under the hood of your KB7, you might consider placing the radiator behind the cab and having the intercooler in front of the motor where the OEM radiator was installed. This may be interchangeable.
I bought an IHC R150 frame for my R crewcab project. There will be some simple fabrication for the suspension and less difficult fabrication for the Cummins 5.9 24 valve. This frame must accommodate a set of DANA 60 axles and sir springs. My thinking is it may be easer to mount an IHC cab and running boards onto and IHC frame. The frame was designed to match the cab.
This frame is 246 inches long. the rear of the frame can be shortened, if required.
I am not a fan of frame swaps, usually. There are circumstances where the frame swap is a good idea, and other times it is thought to be an easy way out of a situation. A frame swap, in your circumstance is the best way to get what you want done safely and reliably. Good Luck