Amazon.com: Graphics Video Card GPU Replacement for Apple iMac Mid-2010 A1312 Core i5 3.6 MC510LL/A MC511LL/A 27 Inch 27" Desktop PC Computer, ATI Mobility Radeon HD 5670 GDDR3 512MB Genuine Parts :
iMac Intel 27" EMC 2374, AMD Radeon HD 4850 Video Card Removal & Repair - iFixit Repair Guide
For iMac 27" A1312 Mid 2009 2010 2011 6970M upgrade NVIDIA GTX 860M Video Card | eBay
Amazon.com: Valley Of The Sun Genuine Graphics Video Card Replacement for Apple iMac Mid-2010 Core i5 A1312 27-Inch MC511LL/A MC511 Desktop PC, ATI Mobility Radeon HD 5750 GDDR5 1GB MXM VGA Board
Amazon.com: Valley Of The Sun Genuine Graphics Video Card Replacement for Apple iMac Mid-2010 Core i5 A1312 27-Inch MC511LL/A MC511 Desktop PC, ATI Mobility Radeon HD 5750 GDDR5 1GB MXM VGA Board
SOLVED: What GPU's are compatible with iMac 27" 2011? - iMac Intel 27" EMC 2429 - iFixit