Light-duty truck buyers interested in purchasing a half-ton diesel are going to have to wait until after 2010 at the very earliest. GM is the latest manufacturer to confirm a diesel engine won’t be offered any time soon in its light-duty pickups. Employees at GM’s Tonawanda Engine Plant near Buffalo, N.Y., were told Monday that the all-new 4.5-liter Duramax V-8 diesel has been indefinitely postponed.