iMac 2009 to 2011 (A1311/A1312) Upgrade Guide – MacintoshMen
Amazon.com: Valley Of The Sun 2GB Graphics Video Card Upgrade for Apple iMac Mid-2011 27 Inch Core i5 MC814LL/A MC814 A1312 Desktop All-in-One PC, AMD Mobility Radeon HD 6970M Replacement Repair Parts :
How to Upgrade/Replace GPU Graphics Card on Mid-2011 21.5" iMac - YouTube
Amazon.com: Valley Of The Sun 2GB Graphics Video Card Upgrade for Apple iMac Mid-2011 27 Inch Core i5 MC814LL/A MC814 A1312 Desktop All-in-One PC, AMD Mobility Radeon HD 6970M Replacement Repair Parts :
Today picked up a $20 2011 iMac 27” with working gpu too! : r/mac
Upgrading the graphics in our 2011 iMac (first attempt) - YouTube
Amazon.com: 2GB Graphics Video Card Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, ATI Radeon HD 6970 GDDR5 2 GB, New GPU Upgrade Repair