i really don't know honestly lol. when i look up the part #'s i posted on subaru genuine parts they both come up the same price.
when i look up the sti specifically on opposedforces i keep getting the 2 part #'s i previously posted.
when i look up a regular impreza or wrx (not sti) i'm finding the 2 part #'s you posted.
you sure your diff carrier is off an sti?