Two consortia have been shortlisted to deliver major upgrades to the Augusta Highway with the Joy Baluch AM Bridge duplication and Port Wakefield overpass.
CPB Contractors, Aurecon and GHD have been shortlisted, as has Lendlease and KBR.
The preliminary announcement also covers a planning study and construction works for a jointly funded section of duplication on the Augusta Highway.
Duplication of the bridge is expected to significantly improve safety for both vehicles and pedestrians while also benefiting efficiency and freight productivity.
The bridge, part of the national road network, is a critical link between the country's western and northern areas and the eastern seaboard as well as metropolitan Adelaide.
Member for Grey, Rowan Ramsey, welcomed the news and said he was pleased to see the projects progressing.
"These improvements will be enormously beneficial for both locals and visiting motorists," he said.
"The projects will increase road safety, reduce travel times and provide safer overtaking opportunities, delivering more efficient and reliable travel."
Deputy Prime Minister and Minister for Infrastructure, Transport and Regional Development, Michael McCormack, said the projects were an investment in the region's economy.
"When complete, these projects will improve freight connectivity and reliability for South Australia's key regional industries, lowering business costs and encouraging investment and jobs," he said.
"They will also reduce congestion during peak holiday periods, supporting the tourism economy."
State Minister for Transport, Infrastructure and Local Government, Stephan Knoll, said the procurement would ensure best project outcomes.
"Importantly, this procurement model will ensure local small to medium enterprises are given the opportunity to deliver key aspects of these important projects, under the main works contract," he said.
CPB and Aurecon have previously worked together on the Torrens Road to River Torrens project (T2T), Seaford rail extension and Goodwood rail junction rail grade separation, while GHD has also worked on the T2T, as well as the South Road superway.
Lendlease and KBR have collaborated on the Southern Expressway duplication, Lendlease is also delivering the North-South corridor and Northern Connector project and KBR worked on the Torrens rail junction project.
The projects combined are worth $290 million and are jointly funded, with 80 per cent contribution from the federal government and 20 per cent from the state government.
Major construction works on the Joy Baluch AM Bridge and Port Wakefield overpass and highway duplication projects are expected to begin in 2020.
The bridge duplication is expected to be completed in 2022.