The TD04 turbo (sold by Subaru, actually manufactured by Mitsubishi) is factory-issue on the 2008 WRX and 2005-2007 Legacy GT/Outback XT. It's a direct bolt-on for those cars.
This OEM Subaru WRX turbo will NOT bolt to pre-2008 WRX cars, nor will it fit the 2015+ WRX.
No core required.
Fits all 2008-2014 Subaru WRX (although it would be a downgrade for the 2009-2014 WRX, which came with the larger VF52 turbo), and 2005-2009 Legacy GT/Outback XT.