It is flashable if the device id is 200.
I think that card is device id 200, but you should check. Can be done from either Mac or PC.
If it is 201 or 202 you will need to treat it as a Titanium card, since that is what it is. See my brilliant expose here.
If it is 200, you can use any of the ROM images to flash. I have never been able to do it from a Mac, would LOVE to be wrong.
Latest ROM for a GF3 is 1057 from "Nvidia ROM Update" available from Apple site. Open package with a right click (I said it) and dig out ROM folder.
Until we figure out on a Mac, must be done with "NVFlash" on a PC in DOS.
dp