I've been researching an engine swap for my '04 and I've found lots of interesting information that has me leaning towards a 5.9 swap. A lot of it depends on exactly what you want to accomplish and what your emissions requirements are.
1) It's been rumored that you can run a hemi with the 4.7 ECM. The computer doesn't know what engine it's connected to, only what signals it receives. So if you can get the crankshaft and camshaft position sensors to send the correct signals you'll be golden. This is actually what I'm looking at for a 5.9 swap. I think this is the tidiest option, though it does have its own complications. But I haven't found an actual example of this yet, just a lot of, "my cousin's brother has a friend who knows a guy who..."
2) It is possible to run other engines with a GM ECM. There is at least one company that sells a standalone harness and the necessary sensors to make an LS computer work on other engines. I didn't look too far into it myself. This is kind of related to the first point, the computer doesn't know what engine it's connected to. The advantage of this idea is that the LS computer is much more adaptable, the code has been cracked and it's easily programmed to work with blowers, nitrous, or whatever.
3) The standalone options mentioned in the previous post will work, but none of them offer OBDII compliance. None of the aftermarket suppliers have the resources to jump through the hoops required for OBDII, especially since they don't know what engines or vehicles their gear is going on. That may or may not be a problem where you live, but you need to be aware of it.
4) If you really just want some extra power it may be simpler to bolt on a blower rather than swap engines. I don't have the link handy at the moment, but I did find a company that sells a kit to put a GM 3800 blower on the 4.7L. It doesn't make massive boost, but anything's better than the stock engine. The kit is around $4,200 USD, not sure what that might be with shipping to Oz. But it could be cheaper than a swap.
One good thing is that your '02 is old enough that it has an ECM still instead of a PCM. That might simplify whatever swap you do. But I don't know what information the ECM might be looking for from other control modules. It was '05 or '06 when Dodge mashed the ECM and TCM together into the PCM. That's something else to consider when you go looking for parts. Lots of people, including most of the vendors I've seen, lump the ECM and PCM together. They are different things. I still can't find a definitive answer whether the manual-equipped ECM trucks even have a Trans Control Module or not. I don't see why they would have, but who knows.
If you don't need OBDII, I'd recommend one of the standalone ECMs mentioned previously and either the 5.9 or the blower kit for your 4.7. Either the 5.9 or the hemi should bolt to the NV3500, not sure about the input shaft though. I say 5.9 over the hemi for the same reason given earlier in the thread, it was a stock option so the parts should be readily available. Granted, the hemi came out in '03, so it might be just as simple. But the 5.9 might be easier to find since it was around for decades as the 360 before they went all metric. Cost is the deciding factor for me. I can get a 5.9 for $250, complete and running. A used hemi will set me back 3-4 times that.
If you need OBDII, you're stuck with an OEM computer. That means you'll have to decide which engine you think will be easier to fit to all the other electronics.