What are you planning to do for engine management? Stock SS harness & ecu? WRX harness & ECU? Standalone? What is your budget and HP goals?
Are you going to use stock heads or do a head swap? What internals are you going with? A stroker kit is the way to go if you have the $$$. For that you will need a new crank, pistons, rods, bearings, and a lot of machine work.
You will need to do a wiring harness merge at the very least. You will also need a new exhaust system and a WRX or SS crossmember for the downpipe to clear.
You'll need upgraded brakes, suspension, and swaybars, and it wouldn't hurt to install new motor and tranny mounts. New axles woudln't hurt.
A stock legacy tranny won't hold up for long with a lot of increased HP.
Read the turbo swap FAQ: http://legacygt.com/forums/showthrea...ps-167968.html
Keep us posted! I have a 22T that I am working on as well. And I love my stock 22T that is in my SS.