Ford Motor Co said on Wednesday it is adding 1,550 workers at four plants to build the new aluminum body F-150 pickup truck. The company also said that for the first time it is promoting union-represented workers from the lower entry-level wage to the pay veteran plant workers make. Between 300 and 500 workers will have been promoted by the end of the first quarter, Ford said. In 2007, the United Auto Workers union and the three major U.S. automakers including Ford agreed that new hires would be paid at a rate less than veteran UAW workers.