The new boss of General Motors has pledged to go “deeper, harder and faster” in a restructuring aimed at saving the ailing carmaker as decisions loom over plant closures and the future of the supersized car brand Hummer. At a press conference in Detroit, chief executive Fritz Henderson said he would prefer to avoid bankruptcy but that a filing was “certainly more probable” than before the Obama administration rejected GM’s recovery plan. “Our preference would be to use the next 60 days to accomplish [restructuring] out of the court process,” said Henderson.