Thanks for all the reading tips. I cleaned off all the black gunk from the GPU and under the heat sink. When I dry fit the fan back onto the MB, it fits snugly over the GPU. There's a copper shim that fills the gap so it doesn't look like there is any room for a 2mm thermal pad, or even a 1mm. Is there a special compound like the original or can I just use the white thermal grease? The top of the GPU is flat and smooth.
A31/P, R51, all FlexView; X20(2), 390E, 240X(2), 600E/X, 570E(2) ,765D, 760ED, more docks than Norfolk & more on the way