<FOURTH NATIONAL CORP> STAKE ACQUIRED Fourth National Corp said an investor group led by management has acquired a 73 pct stake in the company from Interfirst Corp <IFC>, a Dallas bank holding firm. A Fourth National spokesman said the deal was for cash but would not disclose the amount. Fourth National, a bank holding company with about 500 mln dlrs in assets, said in a statement that it will continue to operate its four subsidiaries and retain its employees.