I see no reason to consider replacing a major component on a car you do not own.
Pay the car off, replace the parts you've installed with the correct Subaru parts, and sell the corrected car separately from the imitation ("aftermarket") parts. This will yield you the most $ all said.
Then go buy a car you like instead of this one, that you do not.
If you insist, visit a local wrecker and price a gearbox, driveshaft, pedal set, master and slave clutch cyls, and see if you can get any $ for your existing stuff (and the ECU that goes with automatics).
I would not do this. The car you want already exists in the state you want from the factory, there is no reason to DIY. (Example: The Subaru SVX was not sold with a manual gearbox; it came with an automatic that was less than rock solid. The cars are becoming increasingly rare, and there are no 5spds. In this case a swap makes some sense. In yours, I don't see the logic; the cars are not rare).