Can it be done safely? They each have the same stock cooler, and it has heat pipes actually, all it would need is a multiplier boost and maybe a voltage boost if the 8320 doesnt have the save voltage of an 8350. But I'm just weary of ever using the stock cooler with any sort of over clocked even if its just to the clocks of the same chip just clocked higher because thats how its sold.
Not on a stock cooler.
It is perfectly doable on an after market cooler like the EVO 212. I see your reasoning but the 8320 pats are binned lower than the 8350, while the same chip the ones that became the 8320 would have kicked out more heat or not been up to their standards at the 8350 speed. So yes you can and it will work but the heat will usually be too much for the stock cooler. Get a better one and away you go.
It's possible to have received a chip that wasn't binned correctly and can actually pull off that multiplier with the native voltage, but it is unlikely. The FX 8320 typically maintains a similar overclocking potential to it's big brother, the FX 8350, but it must do so with a more competent cooling solution, as the TDP will be higher due to inefficiencies which resulted in its binning.
It's all about the silicon lottery, but I wouldn't feel comfortable betting on it.