Documents at the center of a Ford lawsuit about a website reveal that the automaker is developing technologies to improve the fuel economy of its trucks by as much as 15 percent and meet tougher proposed federal auto-emissions rules. Ford is suing a website operator who posted the detailed documents online, saying they were stolen. The documents have been removed from the site following a court order last week, but not soon enough to save Ford some headaches. The public airing of Ford’s plans could tip off its competitors, and environmentalists and regulators could use the info to argue that the automaker can meet stricter fuel-economy and emissions regulations, though Ford and other automakers have claimed that such improvements would be costly and difficult to achieve.