The IHI VF46 Turbo is factory-issue on the 2007-2009 Legacy GT and Outback XT. It's a direct bolt-on for the 2005-2006 Legacy GT/Outback XT. (Note that if you are installing it on a 2005-2006 car, you'll want to swap over the little bit of plumbing from your old compressor housing, which contains a restrictor pill.)
No core required.
Fits all 2005-2009 Legacy GT/Outback XT.