In 1977 NZR decided to rebuild 30 of the later Phase III GM Canada-built DA class locomotives into the EMD G22AR model to become the DC class. Over seven years, 80 were rebuilt by Clyde Engineering in Adelaide, while a further five were rebuilt at Hutt Workshops using a mixture of components built at Hutt and Clyde. The first few were shipped directly to Port Adelaide, but after the Union Company withdrew its roll-on/roll-off services, most were shipped to Melbourne's Appleton Dock and hauled to Adelaide via the Victorian and South Australian lines.