Amazon.com: Valley Of The Sun New 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 :
Today picked up a $20 2011 iMac 27” with working gpu too! : r/mac
SOLVED: What GPU's are compatible with iMac 27" 2011? - iMac Intel 27" EMC 2429 - iFixit
Amazon.com: Valley Of The Sun 2 GB Graphics Video Card GPU Upgrade Replacement for Apple iMac Mid-2011 A1312 27 Inch Core i7 3.4 i5 3.1 Desktop Computer, New AMD Radeon HD 6970M
For iMac 27" A1312 Mid 2009 2010 2011 upgrade NVIDIA K4100M 4GB GPU Video Card | eBay
For iMac 27" A1312 Mid 2009 2010 2011 upgrade NVIDIA GTX 780M 4GB Video Card | eBay
Amazon.com: Valley Of The Sun 2 GB Graphics Video Card GPU Upgrade Replacement for Apple iMac Mid-2011 A1312 27 Inch Core i7 3.4 i5 3.1 Desktop Computer, New AMD Radeon HD 6970M