My favorite program is RivaTuner. It allows you to set insane speeds and other really cool features. On my Viper V770nonUltra (125/150 stock..or 143/150 stock...can't remember), I am hitting 160/220, which gives me about 1750 3dmarks (2001). I'm not sure where to find RivaTuner, but if you can't find it, I'll zip it all up and throw it on my website for ya. However, I am using a Blorb on the chipset and some ThermalTake ramsinks on one side of the card. The other side will soon have my custom heatsinks from a cut up 486 heatsink. Before the extra memory cooling, I was able to hit 205 80% stable, 200 100% stable with artifacting, 190 100% stable with no artifacting. I now use it at 220mhz with very slight artifacting and 100% stability. I really don't remember what the core was at before I threw the Blorb on (bout a year ago) because the damn thing was getting so hot I never really tried to OC it. Actually, I will be attaching the Blorb with some better way than the double-sided tape it has.
Also, if you want to find the specs of the memory on your card, you can send me the numbers and I'll decode it for you. Mine on my V770nonUltra is rated for 166mhz, but is stock-clocked 150mhz from Diamond, so actually I was not overclocking the memory until I passed 166mhz. To decode the memory information, I will need the first 2 lines of characters, complete.