You will be safe using the Overdrive utility to overclock and stress test. The warmest mine got using the Overdrive stress test was 62 degC clocked at 4.8Ghz. After many hours of gameplay, temps get up to 50 degC max. Never seen it go higher than that while gaming. Its very rare for any game to push your processor harder than the Overdrive stress test. If, for some reason, your CPU gets too hot, it will automatically throttle the processor to prevent damage.
So yes, you are safe.