I thought only the Voodoo3 2000 AGP had a 300 Mhz RAMDAC. The PCI version of that card which came out a lot later had a 350 Mhz RAMDAC as well, like the 3000 AGP/PCI versions, if I remember it correctly. Its hard to verify this since the 3dfx.com site doesn't have the information regarding these cards anymore. Anyway, the price difference between the Voodoo3 2000 and 3000 PCI is so small that you might as well for the 3000 PCI version. Also, from what I've seen, its easier to find the retail version of that card online as well.
Edit: I just confirmed that all Voodoo3 2000's have a 300 Mhz RAMDAC and all Voodoo3 3000's have a 350 Mhz RAMDAC. Sorry about that. Definately go for the Voodoo3 3000 PCI, it can be found for 90 bucks online. Another alternative would be the Voodoo4 4500 PCI (32 MB RAM), which sells for around 125 bucks online, and also has a 350 Mhz RAMDAC.