Whyalla businessman Peter Seaford was brutally murdered in his own home in the early hours of March 12, 1989 with the takings from the service station he part owned also stolen.
Police are calling on a person who contacted Crime Stoppers last month with some information about the death to make contact with them again.
"It would be of great benefit to the investigation if the person who provided this information was to make further contact with us," Detective Senior Sergeant Schneemilch said on Sunday.
"They can do that via Crime Stoppers, or by calling Major Crime directly."
Police believe Mr Seaford may have been killed after he fought with an intruder, pulling off a home-made balaclava and possibly identifying his attacker.
"The injuries he's suffered show this was a sustained attack and he's fought back," Detective Schneemilch said.
"He had quite a lot of defensive wounds on both arms."
Police believe there may have been more than one person involved in the murder and have positive lines of inquiry, but say there is still a lot of work to be done "to join the dots".
A person made contact with Crime Stoppers on 17 February on the website and provided information that suggested they have knowledge about the murder.
A reward of up to $200,000 will be paid by the SA government, at the discretion of the police commissioner, to anyone who provides information that leads to the conviction of the person or people responsible for Mr Seaford's murder.
