Definitely has headroom like Louis says. 72°C is the max safe long term temperature for maximum lifespan (10/15 years), but if you hit 75°C don't worry. Most OCers won't worry about temp till they hit 90's since that's where you start seeing more immediate damage with the emergency shut down temperature being 98°C. They'll run at 85°C the entire time and the chips lifespan will usually be halved because of that.
Even if it's not a unlocked chip, as long as it's on a over clock enabled motherboard the base clock can be adjusted to raise the GHz . Bad news is that the 2600 does not like its base clock being changed at all. The default base clock speed for it is 100mhz and you'd be lucky if it'd go up to 105mhz. Maxing the chip out at 3.57Ghz.
Personally isn't worth it to me, but if you really want to squeeze that tiny bit of performance out of it try this. 1st- set the voltage to 1.3V. 2nd- Nudge the base clock up by one, restart and boot into windows, test if stable, and then keep repeating till it becomes unstable or you reach 105 base clock. 3rd- done, but notify us of results on the page so we can see if we helped any.
99% of the time, I edit for type-o's and grammar. I'll note it if that's not the case.
I write near essays for most my responses, and then try to condense as best I can to the introduction of one. Less is more. Let me know if I post to much.
I do a lot of spacing for readability. Let me know if that makes my posts seem to big.