Yeah, the 660M should work, but I asked him as well.
He said macOS wouldn't boot, but I am unsure why - all he said was that he replaced the dead GPU with a 660M from a different board (didn't ask if it was from a different iMac or what other device).
By my logic, a hackintosh would work as...
this might sound weird but I found a good deal on a used iMac from 2009 / 2010 with an i7, 6GB RAM and a 500GB SSD.
Problem is, it only runs Linux because it got repaired.
The GPU was dead so the owner replaced it with a GTX 660M.
He says that macOS won't boot anymore, but since it's...