How many players who have hit 40 home runs in a season have had exactly four letters in their last names?

Nine players with four letters in their last name have hit 40 or more home runs in a season. They are (with year(s) they hit 40 home runs):

American League
George Bell – 1987
Norm Cash – 1961
Jimmie Foxx – 1932-1934, 1936, 1938
Jim Rice – 1978
Babe Ruth – 1920-21, 1923-24, 1926-32

National League
Willie Mays – 1954-55, 1961-62
Johnny Mize – 1940, 1947-48
Wally Post – 1955
Sammy Sosa – 1996, 1998-2000