There are a couple of things which I believe would make it so I wouldn't do that:
- More than likely, even though they are the same base engine (6.1L Hemi), they are still tuned differently. The variance in the tunes could introduce unforeseen problems.
- If it is a bad PCM, how do you know if whatever caused it to happen might not do that to the swapped in PCM? It really doesn't make sense to have two vehicles down with the same problem.
Then there's the rub: Will it even fit? I'm not sure on the Chrysler products, but am wondering if the wiring harness will have mating one with the other, which means you wouldn't even be able to get it into the vehicle in the first place to try.
If it's something which you really feel you need to test, buy a used one from eBay or Craigslist. I wouldn't put a known good one which you still need in danger just to prove a diagnosis.
On a separate note, P0301 and P0304 are misfire codes (obviously). Try moving parts around on the same vehicle (ie: move the coil(s) for cyl #1 to cyl #2) and see if the code follows the cylinder. I would mistrust the diagnosis on the parts before I'd believe it to be the PCM ... mainly because its a lot cheaper to change out the coils and/or plugs than it would be to get a new (or even used) PCM. Just a thought.