Bob Gibson >> Steve Carlton.
Remember that Gibson's 1968 year mandated that the pitcher's mound be trimmed to compensate...
Having Koufax and Gibson as 1,2 would be quite intimidating to any and all AL All-Time batters.
Here's Gibson's 1968 stats. Note how he pitched all 9 innings of 3 out of 7 games in the World Series!
Given his penchant for aggressive/head hunting, the first AB between him and hunched-over Rickey Henderson in the All-Time Game would be quite interesting...
If Gibson beaned Rickey as a warning shot, would Ty Cobb lead the charge of the AL storming out from the dugout??