start increasing your bus speed from 100 mhz up. Fast enough ram will start to be a problem, and harddrive and other things don't like being clocked to fast. The magical number is 133 mhz bus. Good luck.
I got it up to 522 on a aopen ax6bc, running at 118 Mhz. With my 'old' PII 350 i could run 133MHz easy, guess the PIII is not to happy with these settings, but i guess if you bump voltage a little it should run just fine. Shouldn't let the temp reach over 35C.
i have a Giga-Byte BX-E , PIII450 ,128 PC100 Rams , SB live , 3com 3C905b-TX , Scsi Controller , Fritz Card PCI and a Viper 550 !!
and my PIII450 run in the 4 month @ 558 with 4.5*124 and 28 Grad Celsius !!!!! and i have no problems !!
the only thing i do , is to install 5 fans in my case , 1 on my Viper and 4 on my CPU !!!