The cummins is ALOT easier to swap than a PSD, all it needs electrically to run are the starter, intake manifold heater, and fuel shut off solenoid.
If you do decide to do the swap, use a 12 valve Cummins, not a 24 valve unless you want to swap the pumps, as the 24 valve uses a semi-electronically controlled pump.
From what I have been told, the sensors off of the IDI can be either screwed directly into the Cummins, or with the use of adapters can be made to work. This saves a lot of work on modifying the factory harness on your truck.