Man, that's one of the coolest and fun custom paint jobs I've ever seen on a guitar - front & back - what a steal since it plays well, congrats! 68-75 LPs are tougher to pin down on serial number, here's a good link if it's still legible after the painting.
https://truevintageguitar.com/blogs/tvg-blog/how-to-date-a-vintage-gibson-les-paul-guitar
You might want to reach out to Gibson & ask them - it's unique enough (and VERY 70s) they might dig a little and even give it some press. It would be utter blasphemy to do this today to an unmodified 50 year old LP, but I'm betting it was painted in the 70s when they weren't revered, it was just a Norlin era average guitar. I gutted all the electronics, hardware & added a mini toggle switch to my 79 LP standard in mid 80s with zero thought about value or keeping it original, only paid $250 for it.