Just in time for Earth Day, Al Gore is trying to burnish his green image. Today he travels to Detroit on behalf of the administration to announce a new deal under which heavy-duty engine and truck companies will produce more fuel-efficient buses, trucks, and 18-wheelers. Monday he announced new proposed drinking water rules. Tomorrow, Gore will address a crowd gathered on the National Mall in Washington, D.C., for a big Earth Day fair and rally. And to mark the 30th anniversary of Earth Day, Gore’s best-selling 1992 book “Earth in the Balance” is being reissued with a hard-hitting new foreword. Gore’s opponent in the presidential race, Texas Gov. George W. Bush (R), is seen as having a weak record on environmental protection, though he is attempting to paint himself as a moderate on the issue.