When you look at McCovey's numbers in the 60s, they are all the more impressive when you consider the game back then was slanted towards pitching and not hitting- the strikezone, mound height, pitcher-friendly ballparks, particuarly 1963-1968.
And his own ballpark, Candlestick, with the unpredictable winds before it was enclosed.
Imagine if interleague play was around and McCovey got to play a handful of games at a hitter friendly place like Fenway Park or Tiger Stadium.