My wife and I actually were on that GB36 yesterday! Really nice, considering it is almost 40 years old, but still in good shape, except: as you pointed out, no generator or inverter, also no a/c.( It did have wiring for a genset, though.) IMO it needed to have the bottom scraped and painted, but the biggest issue was the teak decking; it looks okay, but has worn well below the level of the thiokol, so refinishing or replacing would be a big deal. Even if there were a good way to put down new strips on top of existing, you then couldn't get to the existing bungs and screws. I guesstimated that all the above could easily run $80-$100K, at which point we would have a nice boat, but really expensive, and still 40 years old. I had not been on a GB for a while, though, and was reminded that they are really built solid, and the light and layout is great; it feels much more spacious than some other 36's. Also has good tankage, good space and access in the engine "room", and the quality and construction of the mast and hinge are almost worth the price themselves!
But we will continue looking...