I looked into this when my forester exploded (literally shot the rod through the case) you would need the series 2 2.2 in order to swap into a series 2 2.5l single overhead cam and then just swap intakes and sensors. The dual overhead motors have significantly different wiring. If you have a donor car it can be done, but by now I'm sure you can find a direct replacement motor to save a lot more time.
it has signal cam if its the old style 2.2 won't work only thing u can use is the block get 2.2 head gaskets for a signal cam like out of a 00 imp 2.2 that will work