First generation core i5 CPUs are overclocked by increasing BCLK speed. I'm running my i5 760 at 4GHz (20x200MHz, 21x133 default).
You can run all voltages at automatic, even the vcore if you dont feel like manually fine tuning. Just make sure you set up XMP memory profile properly, maintaining the RAM clock at default when you change BCLK, else you'll probably be unable to boot.
Also, if you are getting random lockups and/or BSOD outside stress testing, turn Speedstep off in BIOS.