Stephen J. Girsky, vice chairman of General Motors, says the company has a new emphasis on the customer even as it faces such challenges as industry-wide overcapacity, strong competition from rivals both in the U.S. and Europe, and slower-than-expected sales of the Volt. Wharton management professor John Paul MacDuffie asked Girsky to talk about these issues and others shortly before Girsky’s presentation at the recent Wharton Leadership Conference. The conference also included presentations by former NASA space shuttle commander Jeffrey S. Ashby and John Kanengieter, director of leadership at the National Outdoor Leadership School. An edited transcript of the conversation follows. John Paul MacDuffie: This is John Paul MacDuffie from the management department at Wharton. I’m here with Stephen J. Girsky, who is the vice chairman of General Motors. Steve, welcome to Wharton. Stephen Girsky : Thanks, John Paul. It’s a pleasure to be here.…