I think you would insure it as a fibreglass sailboat built in 1973 as opposed to a specifically rare and obscure boat, at whatever value the surveyor determines its value to be. You should have it surveyed for both your own good as well as the fact that without a survey most insurers wouldn't insure it. Also see sailingdog's "Boat inspection tips" here
http://www.sailnet.com/forums/boat-r...trip-tips.html
Brian