This is from ESPN.com, however it refers to an older time period than what you are asking about:
# Dunlop specially crafted a racket for him, the McEnroe Maxply, which had an angular grip sized 4 5/8 and weighed 13½ ounces strung. Although his racket was strung at a relatively low 50-52 pounds of tension, McEnroe still went through more than 100 sets of gut a year.
I've heard that he still uses gut, but strings it around 56 or 57 lbs.
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Heres are some more tidbits from that espn site:
# Upon McEnroe's arrival in 1972 at Trinity School in Manhattan, headmaster Dr. Robin Lester said, "If you lined up all 300 boys in his approximate age group...and asked us to place them in the order of who was most likely to succeed as an international athlete, John would have come in 299."
# At Trinity, McEnroe had his most success in soccer. As a senior at left wing, he led the team in scoring.
# McEnroe's childhood idol was Rod Laver.
# In 1978, McEnroe, a freshman at Stanford, won the NCAA championship by defeating North Carolina State's John Sadri, 7-6, 7-6, 5-7, 7-6. In what some have called "one of the greatest matches in college tennis," the duel lasted four hours and the difference between their aggregate point total was one (McEnroe 144, Sadri 143).
# McEnroe joined the pro circuit later in 1978. It took him only three years to be ranked No. 1 by the ATP computer - the youngest to be so ranked at 21 years, 15 days.
# McEnroe's first Davis Cup participation came in 1978 when the 19-year-old helped the United States to a 4-1 win over Great Britain. He would compete in Davis Cup play for 12 years, during which he set or shared 20 U.S. Cup records.
# The Borg-McEnroe confrontation at the 1980 U.S. Open final rivaled the confrontation the two had at Wimbledon earlier that year. McEnroe outlasted the Swede, 7-6, 6-1, 6-7, 5-7, 6-4 in a match that went 55 games and covered four hours and 13 minutes, 20 minutes longer than their Wimbledon marathon.
# Dunlop specially crafted a racket for him, the McEnroe Maxply, which had an angular grip sized 4 5/8 and weighed 13½ ounces strung. Although his racket was strung at a relatively low 50-52 pounds of tension, McEnroe still went through more than 100 sets of gut a year.
# In the five months following his 1981 Wimbledon victory, McEnroe's Dunlop Maxply rocketed an astronomical 240 percent in U.S. sales.
# From 1980-85, McEnroe reached No. 1 on 14 different occasions. At the end of every year from 1981 to 1984, he was ranked No. 1.
# McEnroe was the ATP's Player of the Year in 1981, 1983 and 1984. He and partner Peter Fleming were the ATP's Doubles Team of the Year in 1979 and 1981.
# At one stretch in McEnroe's career, he was ranked No. 1 in doubles for a record 257 weeks. He would win 77 men's doubles titles and one mixed (at the 1977 French Open with Mary Carillo).