[Sunroof]

On a 1974 fiberglass hull the chances of having osmotic blisters is high! Example. My 1985 Hunter 25.5 when pulled from Lake Allatoona to Lake Lanier showed over 300 blisters!! It took me many weeks to fix. When they pulled my Catalina 30 out for a survey over 30 blisters were identified. By then I was experienced at repairing them and still bought the boat. Do some research on the subject. Bottom paint on a fresh water fiberglass hull is nuts when you think about it unless you pay for a costly barrier coat. Your only getting algal matting not barnacles or boring worms. Blistering to me can be a deal killer, but that's my opinion. I would agree on other items you mention. I doubt your keel bolts are stainless on a 1974 model. The fairing material from the keel to the hull often crack from rust perforating from the keel bolts down. If the bolts are rusted chances are you have fairing concerns but you would not know this with a boat in the water unless inspected in the water by someone under the water! Thru hulls back then might be gate valves. Much to look at and much to think about.

my 2-cents

If you do not pull the boat then at least have a diver check the bottom or do it yourself with snorkel gear.