So I have a (lifted) 95 legacy. I've swapped its 15mm RSB for a gen 1 OB's RSB (18mm), thus I had the stock legacy bar laying around.
Here's the fun part. I was laying under my wife's 03 OBS and looked at its measly 13mm RSB then thought, "Hmm. . . I wonder"
So I grab the old 95 legacy stock RSB and hold it up. . . . remarkably similar I thinks!!
So today, having her car in the garage since she took the legacy beast to work today (kid seats were in her car instead of mine today I jack it up pull of the RSB from the 03 OBS and line it up with the 95 legacy RSB. . .
Mounting identical, bend for exhaust in the same place, a little longer bend in the legacy one for under the spare tire well, but hell they both have a spare tire well there...why not!
With a couple 14mm nuts and bolts off and two 12mm SB mounting bolts off, I pulled it out and put the 15mm Legacy one in there.
And LO, it mounted right up, with no contact on the bottom tire well!!!
SOOOO, in summary, a gen 2 legacy/gen 1 OB RSB will mount up in a GD-GG (2000-2007) impreza body!
Therefore, an easy RSB mod in these imprezas is to go from the factory (mine's an OBS wagon) 13mm RSB to a legacy 15 or even better, a legacy OB 18mm RSB!! retain the end links with the donor RSB and its bushings, but you can even keep your IMP SB mounting brackets.