Any BP towbar will work, same chassis from 03-09.
This is the case with the vehicles tail lights, unsure whether the same applies to trailer LED tails...
I had a factory fitted towbar on my old wagon, didn't appear to have any flash wiring associated. Might be best to push on and deal with the issue should it arise instead of resolving an issue which may or may not exist.
As previously mentioned, the wheel offset is reasonably low and is what's causing the rub on the inside of your outer rear quarters.
It's the best place to start, failing that there are some other options but would be good to avoid if possible as it sounds like you just want to remedy the issue and are not intentionally modifying.
Speaking from my experience with 4x4s here;
Anything regardless of the overall lift size by way of spacer requires a certification...
Anything with increased ground clearance up to 50mm by way of spring lift (ie. lift springs on factory or replacement struts) does not require a certification.
If you're going to do it, go for a spring lift - far far safer...
Ughhh I can't remember exactly ? you'll be pleased to know that the Legacy struts are 40mm shorter than the OB, good drop there without even considering the springs!
@iludez
Legacy & Outback suspension is interchangeable yes.
You will need to either a) cut the OB bumpstops or b) source some Legacy ones from a wrecker (I've actually seen them brand new on TM too) as even a moderate drop will cause clearance issues there...
Depending on how long you want your tyres to last, I'd recommend getting some adjustable rear camber arms (upper control arms) to correct the camber as even a set of Legacy struts will set you at approx. negative 1.5 degrees.
Other than that you'll be away laughing.
I still miss mine, handled so bloody well with all the suspension upgrades I'd done. Goodluck!