Well i have a P5B motherboard, an e6400 @ 3.2Ghz (2.13 stock), 2Gb of OCZ and an 8800GTS.
I'm running a FSB of 400 and the RAM has 2.1V going to it.
Basically the easiest way is as has been mentioned, slowly increase the FSB from default, and test the stability. You will probably need to give the RAM and CPU more volts if you go fairly high, but the CPU only needs a tiny increase