Before I start, let me tell you that I have almost EXACTLY the same donor car as you
Mine is an 07 without an interior, bent inner tie rods and a single bent rear lateral link. I have put every mechanical bit into my car except for a couple things below.
The driveshaft should bolt up fine. I have the stock STI driveshaft in my car with the 6spd and R180. The only issues I found are this:
1. You need to use rear top hats from a 90-91 legacy if you plan on using the 04+ springs on your struts.
2. I was told by an extremely reputable source that you need to use the stock RS control arms and lateral links. The STI gives you a weird suspension geometry and can also cause some rubbing issues.
3. You *may* need to switch to coilovers in order to get the BBS wheels to fit without rubbing. They are pretty damn wide. I have received conflicting information here from various people who have done these swaps, hence the *may*. I have not tried it myself yet, but will be throwing on my STI struts with COBB springs within the next week or so.
4. You'll need to roll your fenders.
If anybody who has actually done this swap has any corrections, please feel free to do so. All of my information is from a couple extremely reputable sources but I haven't installed all of my rear suspension.