It will not work at all, as the VRM on the chip can not work with 3.3V input. It requires an input voltage that is quite a bit higher than the output voltage. Also, the CPU will always run at 3.3V anyway, as that is what the VRM is for.

Apart from that, the Pentium Overdrive gets the 5V from the additional outer row of pins (that's the only reason they are there). There's no way to even switch these to 3.3V. And if you could, you would have to remove the VRM from the chip and add a bypass. But you gain nothing by doing that.