I have done a few of these upgrades - what is different is the metal frame, the fan(M6497 has four blades), the heat sink, the modem card and the metal pan where the airport card sits. The modem card has a different hole pattern for the screws (which I never install now) and the pan can be easily bent on one corner to fit the new fan but all the parts are easily found on ebay for cheap. One thing that can't be changed is the reset button - located on the left side on the M6497's it is on the back on the A1005's. The pins are next to the fan on the new boards, if you want to have access to the reset button the best way is to extend the wires to the old position. Last thing I can think of, there are a few screws/holes that are different so don't drive yourself crazy if you have an extra screw or are short one.