Capt
I don't like those "Bare 2x4's and ply" at all
What the heck kind of repair or support are they providing?? Something is not kosher here [img]/images/graemlins/frown.gif[/img] I would be very leary seeing that non-marine grade stuff under there. What about the areas you can't see. You could have safety issues here. I would get a professional survey.
Any boat that is 30+ years old needs a transom, fuel tank, wiring and possible floor.(Those hollow spots are a sure sign) If water is getting in those cracks the balsa is absorbing it.
IMHO: There appears to be many issues that have been masked over
I wouldn't pay over $10K for it...