You can find most of this info in any number of forums already, posted for all to see. Some have even made charts that make it easier to search through. OCN in particular has threads with stable overclocks (proven with screenshots).
Most people don't bother messing with the BCLK setting, because it screws with the PCIe, USB, SATA, and other system speeds. It's best to just leave the BCLK at 100MHz and concentrate on multiplier overclocking.
About 70% of Sandy Bridge CPUs get to 4.5GHz. Usually they do this very easily. However, only about 10% get to 4.8GHz. Less than 1% get to 5.0GHz. You can reasonably expect to get somewhere around 4.6-4.7GHz. If you were very very very lucky in the CPU lottery, you might be able to push it higher. If you were very very very unlucky, you might only get 4.2GHz (we have a few on the forums here who are that unlucky).
For a happy Sandy Bridge long-term overclock:
1. Keep the peak Prime95 core temps below 75ºC
2. Keep the CPU voltage below 1.4v