Notwithstanding the provisions of subparagraph (A), and notwithstanding any contrary provision of subchapter A of chapter 63 (relating to assessment), chapter 64 (relating to collection), or chapter 65 (relating to abatements, credits, and refunds) of this title, the provisions of part II of subchapter A of chapter 28 and chapters 35, 36, and 37 (except section
3777) of subtitle D of the Internal Revenue Code of 1939 shall remain in effect until January 1, 1955, and shall also be applicable to the taxes imposed by this title. On and after January 1, 1955, the provisions of subchapter A of chapter 63, chapter 64, and chapter 65 (except section
6405) of this title shall be applicable to all internal revenue taxes (whether imposed by this title or by the Internal Revenue Code of 1939), notwithstanding any contrary provision of part II of subchapter A of chapter 28, or of chapter 35, 36, or 37, of the Internal Revenue Code of 1939. The provisions of section
6405 (relating to reports of refunds and credits) shall be applicable with respect to refunds or credits allowed after the date of enactment of this title, and section 3777 of the Internal Revenue Code of 1939 is hereby repealed with respect to such refunds and credits.