Official temps from AMD FX are 62°C I think. It's hard to find values specifically for the FX-8320 but AMD processors have always been in the 60-70°C range, though i think some of the chopped-down chips were specced at up to 71°C.
The 32nm SOI process used to make these FX chips shouldn't suffer any long-term damage as long as it stays under 90°C but the reason often cited for the low maximum temperature ratings AMD provide is to do with TDP and leakage, in that AMD would exceed their TDP with leakage if they ran at 90°C. Since TDP is more marketable than max operation temperature, they choose to limit the temperature to produce a more appealing TDP value for the spec sheet and sales blurb.
Another factor is the placement of the temperature sensor. Intel's package specification
for Sandy bridge (also 32nm SOI) is 72.6°C but you can find loads of info around the web saying that Tcore
can run all day at 90°C but should never exceed 95°C. That's because the temperature sensor embedded in the actual core will always be in a warmer part of the chip than the integrated heat spreader which is rated at 72.6°C. If you want to apply this rule of thumb to AMD, you could add 17°C to the 62°C rating of the 32nm FX chips and call it 79°C.
I susepct the lack of any obvious answers linking to a page from AMD saying "never exceed this value" is because one doesn't exist.