Sadly it all comes down to the AirPort cards connection.

If you review the one yours has it uses a surface mount, while the newer units use an edge connector. BroadCom the manufacture of the part only made a limited number of AC boards with the surface connector which have long since disappeared to the winds. Apple never contracted them to make a production run of the part so only the engineering samples were available.

So where does that leave you?? You'll need to do some deep digging to try to find one or consider using a dongle. Even with a dongle the amount of performance gain will be slight. And if you where looking at Hand Off services they won't work with the WiFi dongle.