Your main problem is the G31 chipset. The G31/G41 chipset is an economy chipset. You will have difficulty pushing the FSB freq much past 350 MHz. And when you are starting at 333 MHz, that does not leave much room for a significant overclock.
well... your the expert, all i can do is push it as far as i can and make sure to keep it cool too.
ill get a aftermarket cooler and some paste too.