The move, which has been financially supported by the state government, has saved some 320 jobs, although another 40 will be lost in the restructure.
Called Ion, the firm has been in voluntary liquidation since the end of 2004 and has shed some 600 workers in that period.
In addition to whole cast wheels, the company supplies Harley with wheel hubs and swingarm parts.
The Adelaide Advertiser newspaper reported: Harley-Davidson executive Don Gogan, the managing director of the renamed New Castalloy, described the deal as "a milestone" in his company's history.