Is there an 802.11ac Airport Extreme card available for older Mac Pro machines?
The Apple Broadcom BCM94331CD adapter will add 802.11 a/b/g/n with Bluetooth 4.0 to an older Mac Pro, while the Apple Broadcom BCM94360CD adapter will enable 802.11 a/b/g/n/ac support (the primary difference between the two adapters being 802.11 ac).

You can easily DIY by finding suitable parts on eBay or Amazon and following instructions on forum sites such as MacRumors and elsewhere.

If you're running Yosemite and want to take advantage of Continuity, you'd then just need to buy a third-party Bluetooth 4.0 USB dongle that utilizes the Broadcom BCM20702 chipset (e.g. Asus BT400, IOGEAR GBU521, GMYLE 3340).

A far easier — albeit more expensive option — is to install an aftermarket Wi-Fi + Bluetooth "upgrade kit" from either OS X WiFi or MacVidCards, which will add 802.11 a/b/g/n/ac and enable Bluetooth 4.0 LE.

With the necessary hardware requirements met for Continuity, you could then use the Continuity Activation Tool to enable support for your particular Mac model.



You'll then get full native support for all of the new features in OS X 10.10 Yosemite that are part of Continuity, including Handoff, Instant Hotspot and the new AirDrop.