Its a drop-in cept you have to do a lil' fitment for the hvac. The rs dash beam is too narrow for the wrx hvac. And um, duh of course you need the wrx hvac equipment that goes without saying. The main point is, the wrx dash BOLTS ON to the rs beam.
Also, it actually makes it an easier swap using the wrx dash. You then don't have to do as much re-wiring.