Lyndon Johnson had just become our 36th president, Jim Brown was running wild for the Cleveland Browns and Y.A. Tittle was throwing passes for New York at the end of the fall of 1963, the last time the Giants were in the National Football League playoffs.

The neighboring Jets, that upstart expansion team formed in 1960, enjoyed their moment in the limelight when a fellow called "Broadway" Joe Namath carried them to a Super Bowl victory following the '68 season. After losing a playoff game the next year, the Jets, too, were back to mediocrity.

The decade that followed was a bleak one here for pro football fans. The Jets did break even three times, and the Giants' fans suffered through more miserable seasons, including 2-11-1, 2-12, and 3-11 under coaches Alex Webster and Bill Arnsparger.

Both teams finished 4-12 last season and there seemed no reason for optimism this year. Now, astonishingly, both are on the verge of plunging into the playoffs.

The festive mood here hasn't all been triggered by the coming holidays. Today, (WTOP-TV-9 at 12:30 p.m.), the Giants will take on mighty Dallas and a repeat of last year's upset of the Cowboys would leave the Giants in a strong position for a wild-card berth.

Out in Queens Sunday, the Jets can help their city rivals by beating, thus eliminating, Green Bay. More important, a victory would put the Jets in the playoffs for the first time in 11 years.

"We don't mind helping the Giants," said Jets President Jim Kensil. "We don't really consider them any more of a rival than anybody else in the league. We're not in the same conference, we don't play them that often and there are enough fans to go around."

The Jets are in a better position than the Giants because they can clinch a postseason game by beating Green Bay. Even if the improving Packers upset them, the Jets can qualify for the postseason fun if Oakland wins at San Diego Monday night.

The Giants are in the unenviable position of having to beat one of the best teams in football, then waiting for all the pieces to fall into place Sunday.

"We're just happy to still be playing a meaningful game," said George Young, the Giants general manager.

"We lost our No. 1 quarterback (Phil Simms) and we've lost some tough games, but here we are. We're playing well and we're getting better. Our defense has been superb lately."

Indeed, since losing that 30-27 overtime game to the Redskins, instead of collapsing, the Giants have become stronger. They bounced back to beat the then-high-flying Eagles, 20-10, the following week in Philadelphia and also allowed only one touchdown in victories over Los Angeles and St. Louis.

Although all-pro linebacker Brad van Pelt isn't expected to play, Coach Ray Perkins is counting on his defense, led by rookie Lawrence Taylor, a linebacker from North Carolina, to stifle the Cowboys.

"There's no way to judge how the Coyboys will be," Young said. "Although they've already clinched the title, they have a lot of pride and don't lose many. But we beat them here last year (38-35) and always play well against them."

When asked about the fans' reaction this season, Young laughed and said he doesn't get as many letters when the team wins. He said the fans have been very supportive, in contrast to the past.

"It's funny how things have turned out for the New York fans," he said. "It's good for the city and it's good for the league. Everything has been positive this year."

It has been that way in the pubs, too. One of the most popular sports saloons in Manhattan is Runyon's on 50th Street, and bartender Jim Costello was so busy this afternoon he barely had time to talk.

"Everybody's talking pro football." he said. "It's been a long time since there's been this much enthusiasm. We usually run a bus to the Giants games, but tomorrow we got two going and they're sold out. It's more of a party scene when they're winning."

A Giants victory is apt to set off a New Year's Eve type of celebration here Saturday night, but the man who would be most touched probably will be content to light a fresh cigar and sip a little brandy.

Wellington Mara owned the Giants in 1963 when they lost the NFL title game to Chicago, 14-10, and never in his wildest fears expected an 18-year drought. Now, at last, he has reason to hope, but experience has taught him not to base everything on one game.

"It's not going to spoil this year for me if we don't win," he said. "This year I thought if we could be on the upper part of developing, it would be good. Now we find ourselves contending. It's better than burning tickets in the parking lot."