I'm not an expert but I have a 79 and yours looks legit to me. Headstock and logo look good. Looks like it has the three piece neck and volute Norlin was using in 79. I also see the fret nibs and all the aging on the binding and such looks natural and good. If you take off the control panel and see the metal cover underneath that Gibson was using in the 70s I'd say it's legit for sure as I don't think a copy would ever bother with that. If you don't see, don't panic as I think those often got lost or just removed after the pickup covers were removed as the metal cover was for shielding and once you took off the pickup covers you have a grounding issue unless you add a ground wire anyway. In general, I don't I've ever seen a counterfeit 70s LP so I think it's almost certainly real.
You can give this a try to verify your serial number Gibson guitar serial number decoder. Date a Gibson by serial number (serial-number-decoder.com)
Looks like you have a great guitar there. If everything is functional I wouldn't mess with it too much other than taking it to a real luthier for a setup and cleaning.
