Allied Corp. delayed its planned purchase of 22 million shares of Signal Cos. common stock from Friday until July 8 because of a Justice Department request for more time to review Allied's planned merger with Signal . . . National Medical Enterprises reported the acquisition of Assured Investors Life of San Francisco for undisclosed terms . . . MCI International said it will begin providing direct-dial telephone service to Bahrain, Barbados, Malawi, Senegal, Sri Lanka, Taiwan, Tanzania and Tunisia beginning July 1 . . . Montgomery Ward's plan to sell the Northern division of its Jefferson Ward chain to Stop & Shop Cos. has won final approval from all parties, Ward's parent company, Mobil Corp., reported.