I will definitely take a look at that. Thank you for your post.
So.. I checked out the thread that Victrix sent posted above. If you guys want to view the thread, you must register in order to see it; trust me, it is well worth the trouble.
The guy successfully mated a Z33 transmission onto his Phase 1 Ej25 block, if i recall correctly, however, he had to do a lot of cutting and welding.
He was also able to fit in a R200 rear-end and use J30 Nissan rear-brakes by fabricating his own custom axles. He didn't have pictures of this process, however.
The guy knows what he's doing and although he was able to mate the new transmission onto his motor as well as adapting an R200 rear-end onto his car, replicating his build might be harder for people who are scared of fabrication, and the way he did it involved A LOT of fabrication.
For the cleanest installation, an adapter plate would be the most desirable.
This is an adapter plate made by Kennedy Engineering that is capable of mating many different engines onto a Porsche transmission. There are many adapter plates flying around in the aftermarket made for different transmission+engine combos. A Subaru solution, however, has not been made.