Splitting the top and bottom hull is no easy task, and is usually necessary to remove the floor to change the stringers, which apparently have never been done. Odds are the stringers are all soft. Foam then gets replaced and odds are the foam is flooded and adding 300 pounds to the boat weight. Transom will likely be rotted out or very soft, repair when hull is separated. Engine hopefully is not a rebuild as most of the rebuids use automotive components and not the necesarry Marine components resulting in an undersized oil pump, etc. If not, a full rebuild should be done at that age.
Next, take that trailer apart and sand blast it and get it galvanzed.
Finally, you can get really good paint to go over the gel coat, as odds are its all chalked up anyway. Or re gel coat it.
Voila, a just like new boat. Ask Big Zeke. You will end up with a retro boat that will serve you for 10 years, at about 1/2 the cost of new.
Not saying don't do it, I and my brother have both done it. I don't have the time any more, and after the many surprises, I don't know if my brother will ever do it again.
Drewski