Haven't overclocked my Blizzard 1260 as I don't have it any more. I do want to overclock my BPPC sometime though.
Check out BBoAH and go to the Processors section. This will give you some information on how far you can push your CPU, but remember to cool the CPU so you don't break it. Can't see why you shouldn't be able to push it to 66 MHz, even though I'm only going to push my 68060 to 60 MHz, because of the SCSI bus on the BPPC board.
