Two for the Hall

[Copperfields]

On this date (August 4) in the same year (198?), two players both reached milestones that guaranteed their entry into the Hall of Fame. 18 years earlier, both the players had both been selected the Rookie of the Year in their respective leagues.

Who are the players and what were the milestones?

[Demreb]

Tom Seaver won his 300th as a White Sox against the Yankees and Rod Carew got his 3000th basehit.

[Copperfields]

You are correct. I thought it was pretty cool that both guys who started their careers winning the ROY award in the same year ended up reaching such a defining milestone on the same day.