Historical clue formulations

• Much-viewed showdown of 1975 — 2023-05-06
• Big 1975 boxing showdown — 2014-10-08
• 40-Across, familiarly — 2010-10-01
• HBO showing of 1975 — 2007-02-16
• Epic 1975 showdown, popularly — 2006-03-04