I'm in exactly the same boat - can I use the logic board from the next year's model? (I would assume that it wouldn't be a problem since it will physically fit in place). The bigger question is if I can I use my old 3.4 GHz i7 CPU in the newer logic board (that too should work, but...)
Does anybody have the part numbers for the logic boards for this machine (EMC2546) or the late 2013 iMac (EMC2639)? Thanks.