Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, an employee who was first employed by a participating employer on June 5, 1947, and who served continuously from June 19, 1950, to the date of his retirement January 1, 1971, and who is presently receiving a retirement benefit calculated on the final average salary of eight thousand seven dollars and twenty cents ($8,007.20) shall on the effective date of this act have his benefit recalculated using a final average salary of eleven thousand five dollars ($11,005), such benefit to accrue from the first day of the month coinciding with or following the effective date of this act.