The main street in Adelaide in King William Street. Here is a good photo of King William Street with Adelaide's General Post Office in the background, the GPO was on the corner of King William Street & Franklin Street. Turn right at Franklin Street and 200 yards down on the right hand side were the state Ford distributor Duncan & Fraser.
I would say the photo is late WW1 judging by the red cross in the window.
Photo courtesy of the State Library of South Australia B60149.