I'm Cummins swapping a '74 Duster, thought I'd share the progress.
I have some plans to make all of this work, the biggest issue at the moment is figuring out cooling and beefing up front suspension.
The engine itself is going to have to be pushed back a few inches to make clearance for the cooling pack, radiator, intercooler etc.
I'm planning on using the HDK torsion bar eliminator kit and using the QA1 shocks that are recommended and using some relatively heavy springs, at the moment some 325 lb/inch springs seem to be my best bet since they're relatively close to the spring rate of a Ram 2500.
Steering will be handled by the newer borgeson box that has a significantly smaller foot print than the box currently in the car.
Obviously I'm going to have to reinforce the "frame" of the car, planning on connecting the front and rear subframes, I'm thinking the transmission mount I'm going to have to make for the G56 I'll be using will give it some additional strength and prevent twisting.
The plan is to run an 8 3/4 rear end with the tallest gears I can find to actually utilize the limited rev range of the Cummins.
Electrical and electronics are still in the works, but I have some plans for it.