Never sailed either Capricorn or South Pacific.
I think the Capricorn (160L) is a board (see advert from 1989 below) I would like to sail given it has a quattro concave hull. Does it have the stepped vee hull designed by Bruce McKee on the Astro Toy? Can you please post a picture of the board (s) (hull and deck) you have and why you think each or it is no longer "strong or safe" ? These boards had strong and durable PE/PU construction so unless it has been left outside and split in the sun it might still be robust. That said interest in these boards might not be great and you might only get beer money for them. It is sad to see these boards thrown away as they might actually be useable for many people.
You need to decide if you want to sail it as all boards have uses it depends on the winds and conditions you sail in. A light sailor 60-75 kg would have no trouble learning on the Capricorn and progressing in its use. Other heavier sailors might be able to use it as well. If you don't want it, maybe consider to give it away to someone in the "free thread" in NSW.

Bruce McKee says this about the Capricorn: "
While there [Bombora] I designed a few models, one of which (the Capricorn) became so popular that it was Australia's biggest selling sailboard in its first year of production and was kept in production for over twelve years.....My passion in the sailboard design world was to make step-hulled craft (hydroplane) sailboards of various combinations, directed at slalom and the high-speed time trial type section of the sport."
www.mckeesurf.com/?page_id=85The South Pacific (below second picture) had a few different versions (by Mark Paul).
The South Pacific 2 Giant LW Slalom (not pictured) designed by Strapper's Mike Di Sciascio and Tom Luedecke is another board altogether.