In a project that is befuddling industry experts and competitors, Tesla Motors Inc. is looking for possible sites for a giant electric-car battery factory in four Southwestern states. The plant, dubbed a “gigafactory” by Tesla Chief Executive Elon Musk , would be the world’s largest factory by a long shot. Mr. Musk has outlined a proposal to spend $5 billion on it, hiring up to 6,500 workers and creating thousands of ancillary jobs. He compares the undertaking to auto-industry pioneer Henry Ford’s early 20th century Rouge complex. It took in iron ore and other raw materials at one end and rolled out completed Model Ts at the other, aiming to control and cut costs at every stage of production. Mr. Musk wants to begin making batteries at the plant in 2017, a timeline that puts pressure on the company to break ground this year. Tesla executives say they need […]