nice work.. i opted to buy a rampage iv block from frozencpu for $10 bucks tapped new holes and walla.. messed up a bit one of the holes bad drill bit too late.. little bit misaligned as it wasnt in a press it was by drill by eye and hand... but it works just fine it hold the screw so... XD
you need 2mm for the vrm area and 1mm for the chokes..
now, the actual heatsink from factory is quite good like too good as im justifying to put it back instead XD