YPSILANTI TOWNSHIP, Mich. — Rosie the Riveter’s old plant in Michigan has officially avoided the wrecking ball. Yankee Air Museum board chairman Ray Hunter signed papers Thursday making the aviation museum the owner of a 144,000-square-foot slice of the former Willow Run Bomber Plant, where Rose Will Monroe and other workers built B-24 Liberator bombers during World War II. The signing ceremony represented the culmination of efforts to raise the $8 million needed to save part of the factory for the nearby Yankee Air Museum’s new home. The Willow Run factory, which was built by Ford Motor Co.