Just after 10 o'clock on a Tuesday morning in July the call came that a car had rolled off Randall's Island into the East River. Chief Bill Siegel, at his desk at Marine Division Headquarters in the Brooklyn Navy Yard, paused for just an instant then jumped up, grabbed a life jacket and headed for the stairs. Other firefighters were already on their way to the pier where the Kevin C. Kane, was tied up waiting to go. Within four minutes the 52-ft. boat was underway with its five-person crew racing upriver toward the sinking car. The men moved swiftly, yet calmly to set the stern deck pipe to pump water in an effort to gain an extra knot or two of speed. Seventy years ago, fireboats ruled New York Harbor. Much has changed since the first half of the 20th century when the more than 430 sq.