DETROIT—Automotive supplier Gestamp North America Inc. will invest $158 million to expand its assembly plants in Chelsea, MI, and Mason, MI, and invest $700,000 at its North American headquarters in Troy, MI. Its plans include a new chassis assembly line, paint line and press-hardening line in Chelsea and a new 150,000-square-foot facility to house a new laser-cutting cell in Mason. The plants will gain 235 new jobs, while the project in Troy will create 60 new jobs.MORE