Marichal v. Spahn July 2, 1963: pitch counts.

W: Juan Marichal (13-3) 16 innings
L: Warren Spahn (11-4) 15.33 innings

Tuesday, July 2, 1963 Candlestick Park
Attendance: 15,921, Time of Game: 4:10

16 innings.  Giants 1, Braves 0.  Willie Mays hit his 15th home run of 1963; 1 for 6.

Other Hall of Fame players in that game:
Hank Aaron 0 for 6
Eddie Mathews 0 for 2
Willie McCovey 1 for 6
Orlando Cepeda 2 for 6

Tom Tango developed a pitch count estimator.  Tango had two methods:

bPCE - basic pitch count estimator: (3.3 x BIP + 4.8 x K + 5.5 x BB)

xPCE - more exact pitch count estimator

I played with it in 2008: Pitch Counts.  You can read about season and career numbers.

For this legendary 16 inning game:

Pitches per batter faced:
Marichal 3.61
Spahn 3.07

xPCE:
Marichal 217
Spahn 172

Supposedly Marichal refused to leave the game as long as the 42 year old Spahn was still pitching.  I'm guessing that Marichal did not know the pitch count.