Insurance companies already coping with the 1.6 million drivers being thrown on the market by the demise of the New Jersey's high-risk pool say they would have difficulty absorbing the drivers now covered by Allstate when it leaves the state. But the Florio administration insisted that the five years an Allstate pullout would take would allow ample time for an orderly transition. The head of the state's second-largest insurer of New Jersey drivers, State Farm, said today that the departure of the Allstate Insurance Company, the biggest, would "create havoc." "We're stretched out as thin as we dare to be," said Jerry Lane, regional vice president for the State Farm Insurance Companies. "Any idea that we could grab a large block of new business due to the Allstate pullout is totally out of the question."