Ya it most likely would fit, but they are a set. You can't buy just 3rd or just 4th they come from Subaru as a set only. I saw the new parts before they installed them the first time and there was three gears in a sealed bag.
This transmission also already had the newer 3rd in it when I got it. I wish the dealer had given me all of the old parts back. Then I could just have them put the old selector back in and be all set.
I guess the dealer did not see that the trany had already been updated, so they tried to order all of the parts to update it, and some where along the way they did not get the right parts. I would think that a Subaru trained tech should have seen that the parts were not right when they put it together the first time.