Mario Della Torre went missing from Whyalla, where he had worked for BHP.
About six months later a skull and other bones were found washed up on a beach at nearby False Bay.
After an inquest in 1979, then coroner Barry Ahern said he could not be satisfied that the remains were those of Mr Della Torre.
Police began a review of the 54-year-old's disappearance in early 2021 and located the missing man's brother.
A DNA profile was obtained with the results providing "extremely strong scientific support for the proposition that the remains are from Mario Della Torre", a new inquest was told on Wednesday.
"It is my submission that the finding from the first inquest, namely that the court was not satisfied that skeletal remains were those of the missing person Mario Della Torre, should be set aside and substituted with a finding that the skeletal remains are in fact those of Mr Della Torre," counsel assisting Sally Giles said.
However, Ms Giles said there remained no evidence on the available material as to the cause of death.
Deputy Coroner Anthony Schapel will hand down his findings at a later date.
14°C