§ 412. Conversion of federal savings institutions to state charter. The superintendent is authorized to promulgate such regulations as are necessary to permit the conversion of any federal savings association or federal savings and loan association to state charter where such conversion is not otherwise governed by the provisions of this chapter. Subject to the foregoing, such regulations may provide for the conversion of a federal savings association or federal savings and loan association, whether in mutual or stock form, into a state-chartered savings bank or state-chartered savings and loan association. The federal savings association shall submit a written plan of conversion to the superintendent, together with an investigation fee as prescribed pursuant to section eighteen-a of this chapter.