Welcome! I have a 74 SJ I still maintain . The double X bracing is one concern, but the huge bridge plate is probably the real item of sound concern on Gibsons from the Norlin era. I don't know for a fact, but I guess the Bird of that year has such a bridge plate. Like any guitar, but particularly a Gibson from that time, I would have to play it no matter how good the price! The resale value for these Gibsons, though improving of late, has always been low. My SJ does not have socks inside, but it requires the right strings to keep them away and to give it good projection for sure. That Bird in the video sounds good, probably due to the fingers and the recording quality, don't you think? * edit: notice the pins are not factory on the Bird. I bought my SJ new (I'll admit it) and it came with rosewood pins. I went to bone for looks and sound, and have always stayed with such on it.