Replacing the steering rack is a proper PITA, I would not gamble on a used or junkyard rack.  I don't have a lot of NA experience but my understanding is all the MY05-07 cars use the same mounting configuration and are interchangeable, so obviously an STI or Aero rack will be quicker and that's a plus. The earlier MY02-04 racks are very similar and can be made to work though the mounts are a bit different.

If you're replacing the reservoir swap out both curvy hoses and every clamp you come near, do not reuse and of the useless pressure clamps.

I bought a used Aero rack for my Linear to get the quicker ratio but it didn't fit.  Fortunately I checked the mounting before tearing anything apart and I sold it to a local forum member.  To make it fit I would have had to replace the engine cradle and I just wasn't interested in that level of effort.  Changing the rack itself was more than I wanted to do, but I was willing to go *that* far (PITA though it would have been).