Get EVGA Precision X / MSI Afterburner.
Increase the core speed, say +100 and run a benchmark with it... If it crashes out, decrease by 10mhz and try again, if it doesn't crash, up by 10Mhz. Just push the card to it's limits until it crashes, then drop back down a touch. It's as simple as that! (Same with the memory also)
Keep an eye on temperatures etc, but don't worry about frying your card - it won't happen.
Would Heaven 4.0 suffice?