General Motors Corp. is considering a new truck line that could create at least 500 jobs associated with the vehicle giant's assembly plant in Shreveport, La. The state has been negotiating with GM to provide tax incentives. GM is conducting a feasibility study for the truck line. "The economic impact would be tremendous because you would bring in a whole bevy of new suppliers," said Adam Knapp, Gov. Mike Foster's economic development policy adviser, who has been working with GM executives. The company is looking only at the Shreveport plant. "Our Shreveport employees have done a tremendous job of improving efficiency and quality at the plant," company spokesman Dan Flores said. Knapp said GM executives have told him Shreveport is the company's most productive and profitable plant. The truck line in development would be different from the new Chevrolet Colorados and GMC Canyons that GM will begin building in Shreveport in October, Flores said. "We are in the middle of a feasibility study and development of a business case for a potential future investment for some additional truck production at Shreveport," Flores said. "We haven't made a decision." GM invested about $800 million building new manufacturing components at Shreveport for the Colorado and Canyon lines, Flores said.