Jack Nicklaus and Tom Watson, respectively the king of golf and the man who would be king, matched each other stroke for stroke in a scintillating duel today, shooting five-underpar 65s to share a three-stroke lead going into Saturday final round of the 106th British Open golf championship.

Paired together in the third round over the 6,875-yard Ailsa course of the Turnberry Hotel, Nicklaus and Watson turned a gloomy day into an unforgetable one as they accelerated out of reach of most of the other 85 players who began the round, finishing tied at 203, seven under par.

On an afternoon of intermittent showers, when lightning caused a 25-minute suspension of play but the breeze, remained mild enough for the seaside links to be attacked, the pretournament favorites matched strokes and psyches.

Their battle had the feel of match play. The competitiveness all but crackled. You could see it in their eyes, in their strides down the fairways, in the bold shotmaking that seemed to sing "anything you can do, I can do better."

"Seldom do you see that - two guys paired together, in the lead, both playing so well," said Nicklaus, who owns more major titles than any other player in the history of the game. "I was trying to make it a one-man tournament. Tom was trying to make it a one-man tournament, so we made it a two-man tournament. Well, not really, but almost.

At the start of the day, there were 13 players within three strokes of the lead held by Roger Malbie, who was three underpar at 137. Another 13, including defending champion John Miller, were within six strokes.

But a couple of hours after Nicklaus and Watson's 3:15 p.m. tee-off time, everyone except Ben Crenshaw had, for all practical purposes, been eliminated.

Crenshaw - who was tied with Watson after three rounds of the Masters in April, but faded the last day as watson closed out a memorable Nicklaus charge with a 17-foot birdie putt on the next-to-last hole - birdied the last two holes today to finish 66 - 206.

Another three strokes back are Melbie (72), qualifier Gaylord Burrows (68) and Englishman Tommy Horton, who also had a 65 today. That was the record for the British Open until Thursday, when Mark Hayes shot an extraordinary 63, taking on only 23 putts with his recently adopted cross-handed grip.

The Nicklaus-Watson charged overshadowed the exceptional back nine of Arnold Palmer, who shot 37.30 - 67 after changing from a conventional to a cross-handed putting stroke on the seventh hole today.

"The difference was phenomenal. I can't even believe it," said Palmer, 47, the champion in 1961-62, who sounded as if he were back in his glory days despite his three-day total of 213.

Lee Trevino, winner of the British Open in 1971-72 and three other grand slam titles, and U.S. Open champ Hubert Green were tied with Nicklaus and Watson at 138 when the day began. But they shot 72 and 74, respectively, to fall off the pace.

Green never recovered from a disastrous triple-bogy seven at the 355-yard first, where he went ove the green into a trap on his second shot, stayed there, exploded out and over the front edge of the green back onto the fairway, then chipped on and missed a short putt.

Trevino dropped four strokes to par on the front nine. AFter missing a two-foot birdie putt on the par-five seventh, called "Roon the Ben," he double-bogeyed the eighth and bogeyed the ninth, both par-fours. "I hit the putt so badly on the seventh that I was still thinking about it two holes Trevino was also squeamish about the lightning that started when he was teeing off on the ninth, the "Lighthouse Hole" that runs 455 yards from a small tee elevated above the rocky shore of the Firth of Clyde, and later halted play from 5 to 5:25 p.m.

Trevino, Bobby Nichols and Jerry Heard was injured by lightning at the Western Open in Chicago in 1975, and Trevino is only now starting to regain his form after surgery for a back ailment doctors attribute to to loss of muslcle tone cuased by the shock. Heerd's and Nichols' careers were ruined by the accident.

"When I'm at home and I hear thunder and see lightning. I pull the drapes and turn the television up real loud because it frightens me to death," Trevino said. "I'm not being childish. I got hit hard two years ago, and it's like being run over by a train. You don't forget."

To his credit, he pulled himself together, got his putter "Old Mrs. Mayberry" (named after the Winston-Salem, N. C., lady in whose attic he found it in 1974) working, and covered the inland back nine in 33 strokes, birdieing the 11th and 17th. Trevino is tied with Miller, who shot 67 today, at 210.

The way all the potential challengers except Crenshaw fell away gave the Nicklaus-Watson gunfight the semblance of being preordained, and even Trevino was captivated.

"When I looked up and saw Nicklaus seven under, I said, "I guess it's the Golden Bear," he said. "But the teddy bear was awake, also. I think the people are going to be in for some kind of a battle, and that's great."

Nicklaus birdied five of the first 10 holes, brilliant putting more than making up for his tendency today to pull his drives.

But Nicklaus' mastery of the toughest part of the course seemed to inspire rather than discourage the fiercely competitive, Watson, who won the British Open in 1975.

Watson would not let Nicklaus get more than two strokes ahead of him and, after trailing by that margin for eight holes, caught up on the 15th.

Nicklaus three-putted from 40 feet on the par-four 14th, "Risk and Hope," leaving a three-footer on the lip coming back. On the par three, 209-yard 15th, watson put a 3-iron 20 feet from the pin and curled in a tricky downhill putt to get even.

Down the final three holes, they matched each other as they had earlier. Both birdied the par-five, 500-yard, 17th, which has been the best scoring hole throughout the championship.

Watson saved himself on the par-four, 409-yard 16th with a 40-foot chip to within four inches of the cup. He had left a fairrway wedge badly short after outdriving Nicklaus, as he did most of the day.

Nicklaus finally stopped pulling his drives after making a slight adjustment in his head position at the 17th, but missed an eagle putt after hitting his three-iron second shot three feet from the pin. "It was a silly little putt," he said. "I dragged the putter on the backswing and should have stopped, but I was too far along."

They both made routine par-four at the 18th. Watson taking two putts from 50 feet and Nicklaus two from 40 feet. The 6,500-seat bleachers set up in a horseshoe around the greens were packed and the spectators gave both men a prolonged, thunderous ovation.

"That was beautiful. I tell you, it makes you feel great," said Watson, who knows that the Scots appreciate him and Nicklaus more because they won their three British Opens in Scotland. "I felt like I was a baseball player in the middle of the World Series."

Although the overtones of one-on-one were there, neither man forgot that the British Open is 72 holes, medal play, and accordingly pushed each other onlay as far as prudence dictated. "It did seem a little like match play," said Watson, "but we knew there was still a lot of golf to be played. We didn't take unwarranted risks.

"It was fun playing. We both played well. Jack didn't play quite as well as I did, especially with the dirver," added the positive-thinking Watson, "but it was nip-and-tuck all the way."

Saturday, Nicklaus and Watson are again paired last off, for a high noon-style showdown between the top gun and the new gunslinger in town. Club filled bags at 6,875 paces.