Again, the numbers and models are just pure speculation at this point until Nvidia makes an official statement.
I have had 8600's both on my and a friend's dekstop and in my laptop for over a year now and they have been performing well and are staying within normal ranges.
If you are afraid of OC'ing your GPU simply don't and run it at its stock speeds. Oc'ing a notebook is even trickier and riskier because you got less space to deal with heat dissipation. I've seen lots of instances of people overclocking their notebooks and are desperate a few months or a year after looking for advise on how to fix it because they think they burned out their video cards.
Those replacement video cards if found can go between $200-$500 depending on the model.
Bottom line is, overclocking a notebook is not recommended in the long run. You can try in small increments if you wish, but it won't gain you much performance anyway.
You can find the most updated drivers on laptopvideo2go.com
and Fennux's drivers on our NBF MobileForce Driver