Are you overclocking trying to fool around with the gpu for the heck of it, or are you actually trying to play modern games on it?
If it's your main pc and you're gaming on it....I'd strongly suggest an upgrade.
You could get something much better for very cheap on the used market.
For example there's this
https://www.ebay.com/itm/MSI-R9-270...h=item34037819bc:g:pQ4AAOSwdU1caEzL:rk:6:pf:0
But to answer your question, as said in the thread already, as long as there are no issues, you should be fine.
Dangers when overclocking usually come about when messing with the voltage, even if you jacked up the memory and core clock to some high level, it will just crash and probably not cause damage.
Now I'm not suggesting to try that, but you will probably be fine with what you are doing right now.