The on-again, off-again Mary Tyler Moore-Valerie Harper reunion looks like a sure thing now. Filming is scheduled to begin in New York on Oct. 14 on an ABC made-for-TV movie that will feature Moore and Harper as Mary Richards and Rhoda Morgenstern — the classic characters they played in the ’70s on “The Mary Tyler Moore Show” and “Rhoda.” The script reportedly calls for Mary and Rhoda to take up residence in Manhattan and to renew their friendship, while they cope with being parents of grown daughters. No word on any involvement of the Phyllis Lindstrom character (played by Cloris Leachman), who would probably be in a loony bin by now.