The STI wing utilizes 17 holes -- 16 mounting holes and one for the 3rd brake light wiring.
The WRX wing utilizes 5 holes -- 4 to mount and one for the 3rd brake light wiring.
The STI LTD utilizes 5 holes -- 4 to mount and one in the center as a centering point.
None of these wing mounting holes are compatible with one another.
You can either have the holes filled from the STI wing and new ones drilled for the WRX wing or the STI LTD wing; and the STI LTD wing kit comes with a 3rd brake light assembly for installation inside the vehicle cabin on the rear deck.
You can get a WRX wing from the dealer or another member that is selling one.
Or you can see if anyone is interested in swapping trunks from a WRX that has the WRX wing or a WRX or 2.5I that has a wingless trunk.