Adrian - Review these answers [http://www.ifixit.com/Answers/View/131695/Test+the+Wireless+802.11ac+card+in+a+MacBook+Pro+15%27%27+Retina|802.11ac wishers].
The best thing here is to add your comment to the '13 teardown doc so the people at iFixIt see the pent-up want for them to do the needed testing as they have the hardware right now.
As I said before Apple consumes parts at such a rate (as well as contracts for them) new chips and parts like this one will be in short supply for quite awhile. So you'll need to wait until they show up on the open market thats assuming the board will even work in your older system.