If the PCM came out of an '01 it likely won't work. Dodge changed the computer bus, on the Dakota anyways, in '01 to a single wire PCI bus. Your '00 is set up for a two wire CCD bus and they are not compatible.

All your gauges come off of the PCM, they are computer driven.

Check around for an '00 5.9 PCM. They do exist.

 

What if he is extremely lucky, and the build dates are near enough to be the same bus? (unlikely, but hey, always that odd chance)

 

Very unlikely. It wasn't a running change. Just as the interior and transfer case changed in '01 so did the computer bus.