you should try macgregor-boats, or trailersailor forums. lots of mac guys there.
the 70''s are actully venture boats, later to become macgregor,
the macgregor 25'' had inner liners. not sure which year that started.
the early non inner liner boats are ok, but should sell for less.
check the pivit bolt, and centerboard closely. this is a common problem.
best of luck.