This late in the game, there is really no point in overclocking such an old card. Overclocking it may gain you a few extra frames in some really old games, but over-clocking isn't fairy dust, that card, under no circumstances, will play any game on the market today.

3DFX has gone bankrupt since, so finding even an official BIOS for such an ancient card will be a challenge. Good luck in your searches though