You'd need an 04-07 STI driveshaft or an 02-07 Impreza auto trans driveshaft. The front axle stubs need to be swapped so you can use your WRX axles.
Another big issue is the 08+ transmissions do not have vehicle speed sensors. The only fix I know of is from DCCDpro which will convert your ABS signal into a speed signal.
With the CANBUS system, it would be a big PITA to run the engine as is, with the 2010 ECU. Much easier to swap some engine components and run it off an earlier ECU like Alaskan EJ20 was saying.