General Motors Corp. says another six high-ranking executives will retire before year’s end in what it calls the “final round” of senior leadership restructuring.

The paring of executive ranks is an effort to “streamline our leadership team and put some of our best executives in positions where they can use their diverse perspectives and extensive global experience to create the new GM,” CEO Fritz Henderson says in a statement.

Affected by the restructuring:

  • Mark Reuss, former head of GM Holden Ltd. in Australia, moves to vice president-global vehicle engineering, replacing Jim Queen, group vice president-global engineering, and Ed Koerner, GM North American vice president-engineering, GM confirms. Queen and Koerner will retire Oct. 1.
  • Mary Barra, currently vice president-global manufacturing engineering, is named vice president-global human resources. She replaces Katy Barclay, also retiring Oct. 1.
  • Eric Stevens, currently GM Europe vice president-manufacturing, replaces Barra as global manufacturing head.
  • John Buttermore, vice president-powertrain manufacturing, assumes the role of vice president-manufacturing for GM International Operations.
  • Walt Dorfstatter, currently executive director-engineering systems and operations for OnStar, is named general manager of that operation. He replaces Chet Huber, retiring effective Oct. 1. Huber has been president of OnStar since 1995.
  • John Lauckner, vice president-global program management, is named vice president-global product planning.
  • Terry Woychowski, executive director-global vehicle chief engineers, replaces Lauckner in his old job as head of program management.
  • Denny Mooney, vice president-global vehicle systems and integration, will retire Oct. 1. Mooney led GM Holden from 2003 to 2007.
  • Gary White, vice president and vehicle line executive in charge of fullsize trucks, will retire Nov. 1.