Jimmy Connors, hungry to regain his world-beating form of the mid-70s, outdueled John McEnroe, 2-6, 7-6, 6-1, 6-2, today to win the World Championship Tennis final with a performance that was first gritty, then glorious.

Connors, who at 27, has been working feverishly to challenge again for the premier position in the game, was served off the court in the first set, and, by his own account, was "fighting and gnawing and clawing and just trying to hang in there" in the second.

McEnroe began the match serving sublimely, opening up the court so well for easy volleys that he lost only four points on serve in the first set. He still seemed in control when a line call upset him with Connors serving at 5-6, 15-all in the second set.

An argument with the umpire over that call seemed to poke a small hole in McEnroe's concentration. Meanwhile, Connors pumped himself up, held serve, and won the pivotal ensuing tie breaker, 7 points to 4.

With that, the match changed abruptly -- and completely. Connors, rejuvenated, began to wallop his returns and broke McEnroe's serve five times in a row, six of the last seven times he served in the match.

Suddenly McEnroe, who has played too much tennis the past two years, and is nursing a variety of aches and pains, looked weak and weary. His touch and timing deserted him. He began to miss easy volleys and hit late on his ground strokes. his whole game went awry.

McEnroe's first serve took an involuntary leave of absence, and Connors took to launching rockets off his second serve. McEnroe couldn't seem to put the ball away, even on the relatively easy overheads. A half-dozen times Connors got back into points that McEnroe should have ended with a crunch, and twice he returned blazing forehand winners off McEnroe smashes.

McEnroe's first-serve accuracy plummeted from 65 percent in the first set to 59 percent in the second and 39 percent in the third, 50 percent in the fourth. Having served eight aces in the first two sets, he couldn't summon another until he was down 1-3, in the fourth set and fast sinking out of sight.

At the same time, Conners' serve was growing stronger and more accurate: 61 percent in the first set, 64 in the second and 84 in the third, before slipping to 66 in the fourth. He got increasing depth and better placement on his second serves, which McEnroe had devoured at the beginning. No longer could "Junior," as the 21-year-old McEnroe is known, attack them just behind the service line and swoop in to put away easy volleys.

Connors served only two aces, but they came back to back as he held at love for a 2-0 lead in the fourth set. These were full-blooded grunters, exploding down the center line as if to tell McEnroe there was not way he was going to get back in this match.

Connors always has had a shark's taste for blood, and when he got into this match he swarmed all over McEnroe, ripping him apart. What hungry teeth he had today.

At the end, Connors was lashing his service returns and passing shots, getting low and following through on the short, soft shots that often trouble him, pounding every short ball and boring in on the net for slashing volleys, many of them at full stretch.

Connors was moving and lobbing exceptionally well, running down everything, keeping the ball in play until he had the opportunity to uncoil into a shot with furious disdain for the laws of gravity.

The weight and penetration on his shots ground strokes and volleys alike, and the dazzling physicality of his tennis were reminiscent of Connors' glory days, before Bjorn Borg supplanted him as the top player in the game.

At the end, when he received the gold championship cup and the first-prize check for $100,000 (compared with $40,000 for McEnroe), Connors told the delighted audience of 16,181 spectators at Reunion Arena: "Mac wanted to know what it was like when I played in my prime." He grinned. For two sets at least, he had given a grand demonstration.

Connors is the first player to win WCT's eight-man playoff twice since Ken Rosewall beat Rod Laver in 1971-72, the tournament's inaugural years.

"I'm in good company now. Any time I can be compared to Rosewall, that's pretty good," said connors, who was gracious and behaved impeccably throughout the week. Connors' first WCT title came in 1977. He did not play in 1978 and last year McEnroe beat him in straight sets in the semifinals.

Today's victory was Connors' third in four matches this year against McEnroe, and put him on the verge of overtaking his fellow left-hander for the No. 2 world rankings behind the absent Borg, who has not lost a tournament match this year.

Connors made it clear, however, that second is not good enough in his mind.

"There's no No. 2, there's only one number," he said. "I'm not fighting to be No. 2, that's for sure. I'm not fighting to be No. 3. I'm fighting to be No. 1.

"If I want to be No. 1, I've got to forget this now and go play next week (the $500,000 WCT Tournament of Champions at Forest Hills, N.Y., were McEnroe and Vitas Gerulaitis will be his chief rivals) and then to the French, and then to Wimbledon, and then to the U.S. Open.

"Mac and I will play a lot more times, just like he'll play Borg a lot of times and I'll play Borge a lot of times. But I am not fighting to be No. 2. That's the furtherst thing from my mind."

Connors had a disappointing 1979, losing all six of his matches against Borg and three of six against McEnroe as he fell in the semifinals of the year's five most important tournaments: The WCT playoffs, French Open, Wimbledon, U.S. Open and Grand Prix Masters.

It was an unsettling year for him as his tennis took a secondary position. for the first time in his adult life, to, first, marriage (he wed a former playmate-of-the-year, Patti McGuire, secretly late in 1978) and then fatherhood (a son, Bret David, was born Aug. 1. 1979).

Now Connors says he has his family and professional lives separated, and both happily in order. He is working hard on his physical condition and his game.

For two sets this afternoon, it all came together on the medium-pace synthetic carpet at packed Reunion Arena, and at the end Connors stood on tiptoes, thrust his arms triumphantly in the air, arched his back, and gave his old victory salute: A strutting, arrogant impersonation of a proud gorilla.

Asked afterwards if he feels his peak form of 1971-76 coming back, he said: "I'm pretty close. It's not there yet, but I'm working on it. I'm getting there."