Hi all,
After doing some research into the adapter board for the Mid 2011 iMac (EMC 2429, A1312), I have come to the realization that its merely a standard mPCIe to an apple standardized mPCIe connector (I based my research on Pin connector count/Pin spacing). Now I understand that @macvidcards sells these cards at $128-$152 a piece which includes the adapter plus the BCM94360CD card however I think i have found a far cheaper solution.
Amazon.com is selling what they call a "Generic Mini PCI-E Adapter for BCM94360CD/BCM94331CD" which looks to be a simialr design to the macvidcard solution for $18.89 US (with Free Shipping)
http://www.amazon.com/Generic-Mini-...14175659&sr=8-1&keywords=mini+pcie+BCM94360CD
If you pair the adapter with the BCM94360CD which is also available from Amazon.com for $31.98 (with Free Shipping)
http://www.amazon.com/Broadcom-BCM9...TF8&qid=1414176542&sr=8-1&keywords=BCM94360CD
You arrive at a grand total of $50.97 which is $70-$100 off the price if purchased at macvidcard (plus they are currently out of stock). The only caveat to purchasing via Amazon is that it ships from China so shipping time will be 1 week+.
The other concern I have is that the BCM94360CD has 4 antenna ports while the iMac only has 3 pigtails to connect to the card. I have yet to determine if the BCM94360CD has 3 pigtails connectors for WiFi antennas and 1 connector for bluetooth antenna or if the card is supporting 4 spatial stream 802.11 AC (2.6 Gbit\s). In the event that you want to use this card and add an extra antenna to your iMac I found a solution!
Amazon sells a tuned embedded antenna for $12.68 (with shipping included) that supports the 2.4 Ghz (wifi) and 5 GHz (wifi or bluetooth operate at this freq) with the proper connector. The "2.4 / 5 GHz / 2.2dB (U.FL/ IPEX) embedded antennas N/A Antenna" can be placed in the iMac and voila you have all the ports of the Airport card populated!
http://www.amazon.com/gp/offer-listing/B00MHYRV3Q/ref=dp_olp_new_mbc?ie=UTF8&condition=new
So the new grand total with the adaptor\Airportcard\antenna is $63.65. I'm still debating if I really need the new continuity feature, but if I do this upgrade I will post a guide for all users.
FYI, I replaced my 2012 rMBP with the new Broadcom AC card (BCM94360CS) and had great success with the out of the box results. This card may prove to be a better option for the iMac since it has only 3 antenna ports (but is way more expensive).