Historical clue formulations

• Le Mans race unit: Abbr. — 2024-08-11
• Le Mans race unit: Abbr. — 2013-11-05
• Metric distance: Abbr. — 2012-10-28
• See 42-Across — 2008-03-09
• 3,280.84 ft. — 2008-01-05
• About 5/8 of a mi. — 1998-11-04