young kids in the early 80's were still striving for Sandmans, especially vans and by then rust proofing products were coming through and many were getting cars done, especially in areas like the coast. As they were a desireable product a lot of them were also tended a bit more care and hence survived, just like many Monaro's GT's etc. So instead of being sent to the scrap heap a lot were saved, so in my humble opinion this would be why a lot have survived.
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