I would not recommend overclocking the 060, especialy not on the blizzard card with it's original CPU as that is the older and less heat tollerant XC060 CPU. If any I'd say tops 55-60Mhz and then you would need heatsink and fan. It's not a question about if it will work when you turn on the power, but if it will work when you turn on power a few months from now... Rather keep it at it's original speed and have a happy CPU cards for years to come than a 20% speed increase that will only last me a short while before BBQ.
I added feets and a custom trapdoor to my A1200 that offers great airflow and a heatsink for my Blizzard 1260 and it's not even overclocked... just to keep the CPU cool as happy as can be. :-)
I got a 55Mhz oscillator that's suits my machine fine BUT I don't find the speed increas worth the risk. I don't need the extra speed anyway... 060/50 is plenty fast enough for me... need more I just use the CSPPC equipped A4000T instead. ;-)