General Motors (GM.N) on Thursday will announce a multibillion-dollar, multiyear investment in several U.S. manufacturing plants in a move to boost production and vehicle quality, a person familiar with the matter said. GM has scheduled a press conference at its stamping plant in Pontiac, Michigan, to make a “major U.S. manufacturing announcement.” A spokesman declined to provide further details. The largest U.S. automaker is expected to reveal plans to make capital investments in plants and equipment, including body shops and stamping plants, said the person, who asked not to be identified.