It's not just about gpu chip having heatspreader or not. Not even about usually insufficient mounting pressure for gpu-s.
It's about all small factors summed up - you'd be better off with buying universal gpu block since the very beginning without problems of too much pressure, too big block size, unusable mounting sys, and so on and on then spending time and money upon trying to fit something not meant to. You CAN fit car engine on bike. Should you? Are gains in some areas worth losses in others when doing so? Imho - not.