People have hit over 400 FSB with E8x00 cpu's, but they were all using the 1.04g board. And only the 1.04g works correctly with proper vcore settings on e8x00 cpu's; I know 1.02 is limited to auto and 1.45+v, and 1.03 I'm not sure.

You do have to remember that the B2 stepping E6x00 and X6x00's were pretty much limited to between 3.4 to 3.8 ghz on air, and 3.8 ghz often took over 1.5v to get there. If you boot and suddenly get a CPU ucode error during an overclock, its always caused by (1) insufficient vcore, (2) unstable RAM (most likely), (3) unstable northbridge (almost as likely, and can cause very similar symptoms as 2).

I think most E6x00 cpu's could do 3.6 ghz at 1.5v or more.
The B2 steppings were a dog though. The G0 steppings could do 3.8 or even 4 ghz with enough voltage.