Not only does this card us standard six pin connectors so it will work fine in the MacPro, but in many tests it doubles the performance of a GTX 680 Mac edition! WOW!
If I had the money I would totally go for one of these, since it is literally twice as fast as the GTX 680 Mac Edition, and I currently run a GTX 670, though it does have 4 GB of RAM.
I WANT ONE SO BAD!!! Ha! Not happening anytime soon.
Your best bet for one is this one from MacVidCards which is $835 plus shipping, the cards has been flashed for Mac so you get the full startup with it (which I annoyingly don’t have with my GTX 670).