Quote from Samuel Silva:
can I put my imac 20" early 2008 video card in to my 24" imac early 2008 also?
The physical card may fit the PCI-e slot on the main logic board but the heatsink assemply (the pipes etc.) won't fit because the heatsink for the 20" and the 24" are of different shape and different length! You would have to swap the heatsink between the 20" and the 24" cards. To do this requires you to consider redoing the thermal compound on them also! Unless you are an 'expert' in hardware technology, I wouldn't recommend it.