Sections 1.815-2 through 1.815-6, except as otherwise provided therein, are applicable only to taxable years beginning after December 31, 1957, and all references to sections of part I, subchapter L, chapter 1 of the Code are to the Internal Revenue Code of 1954, as amended by the Life Insurance Company Income Tax Act of 1959 (73 Stat. 112), the Act of October 10, 1962 (76 Stat. 808), and the Act of October 23, 1962 (76 Stat. 1134).