So I am considering upgrading my 2010 Mac Pro 2.8 ghz quad to a 3.46ghz six core. I've been reading up on it and found a copy of the service manual. I am especially concerned about the screws. Some indicate that you should count the turns when you loosen them and then turn it the same number when you tighten. The manual not only gives a specific order but seems to indicate that all 5 must first be torqued to 4 inch lbs and then the 4 closest to the processor torqued to again to 8 inch lbs before giving each screw an additional 1/4 turn. I have found some torque limiting screwdrivers on ebay and elsewhere, but I am not sure if there are any screwdriver bits that will fit. It would of course have to be a #3 hex key at 6" long and have a quick change 1/4" drive end. I have found bit sets that include this bit, but the bits almost always have a 1/4" hex shaped shank most of the length of the bit with only the tip finally tapering down to the #3 size. I am not sure what will fit inside the bore on these heatsinks.