Just apply some as3, clamp the sucker on and go slowly, 5mhz fsb at a time. It should be safe I would say, even though its all aluminum. At stock speed, the gc68 should keep that thing around 35C idle, so if overclocked, it should only be 5C higher or so (idle). Maybe at full load, temps might peak from 45 to 50C (depending on how much voltage u give it). But with this heatsink, i would not recommend going over 1.75 volts. Watch your temps carefully too.