It's being billed as a clash between teams with vastly different philosophies and between coaches with vastly different personalities.

But the Philadelphia Eagles would like to think Sunday's showdown with the Dallas Cowboys simply will be remembered as the day the balance of power in the National Football Conference finally shifted from Texas to Pennsylvania.

The Eagles have been building toward this NFC championship game (1 p.m., WDVM-TV-9) from the day Dick Vermeil was named their coach five years ago. The last three years, they've gradually come closer, first progressing into the playoffs, then through the first round and now they are only one victory from the Super Bowl.

"We're ready to play at this level now," Vermeil said. "Dallas has been here before and they are probably better prepared. But this is the biggest game we've ever had. It's what we've been wanting for so long."

And waiting for the Eagles are the imposing, imperial Cowboys.

While the Eagles have been building, the Cowboys have stayed on or near the top of the heap, winning despite the retirement of Roger Staubach, despite the loss of key defensive personnel.

This was the season the Cowboy dynasty was expected to regroup. Quarterback Danny White was no Staubach, after all. And didn't Coach Tom Landry have to start training camp with a secondary almost wiped out because of retirements and injuries?

"My most pleasant surprise, other than maybe the 1975 team," Landry says now about his latest Cowboy club. "I'd have to say that without Roger and those secondary problems, it would be hard to anticipate we'd be this far.

"We had 12 rookies in 1975 and we needed that 'Hail Mary' pass to stay alive in the playoffs. This time, we had that comeback last week against Atlanta. There is no slap at Roger, but he couldn't have played any better than Danny White did in the second half."

One of the few similarities between the teams is their regular-season record (12-4). Dallas is smooth, dignified, confident. Philadelphia is rough, gutty, scrambling. The Cowboys are the NFL's most established dynasty. The Eagles are the new boys on the block, the blue-collar workers of the league trying to scratch their way to the top.

Landry is the patriarch of the estate, dignified and composed. Vermeil is the emotional cheerleader, a scrapper in a green and white sweatsuit who loves a good fight. Landry motivates his players with his cold stare. Vermeil motivates his with the anger in his voice.

As the game has drawn closer. the Eagles have shown the strain. Some players have stopped talking. Others have been curt. Vermeil admits practices have been strangely quiet and tense.

"But we're going to be okay." quarterback Ron Jaworski said. "I think we can win, but that doesn't mean I don't think a lot of Dallas. We know we have to play awfully well to win.

"I know that means I have to play well, but in games like this a quarterback has to play well.The team relies on you to do it. Does that mean I have to pass for a lot of yards? Not necessarily, although 300 would be nice. No, I just have to make sure I recognize their defenses and get the ball where it should go and not make mistakes."

The Cowboys come into the game playing perhaps the best ball in the league. Philadelphia peaked at midseason and has been struggling for weeks. And now the Eagles are aching, especially on offense, where halfback Wilbert Montgomery is limping from leg injuries and there are only two healthy wide receivers.

The fact these teams know each other so well makes this game particularly intriguing. The Cowboys have had fine success stopping receiver Harold Carmichael. The Eagles seem to be able to put the clamps on halfback Tony Dorsett. Vermeil is aware of the Cowboys' secondary ills. And Landry realizes how difficult it is to move against Philadelphia's No. 1-rated defense.

"When you play each other so much, it can hurt you," Landry said. "You start thinking of things you haven't tried before and wind up doing stuff that goes away from your strengths. I know them very well and they know us very well. I don't think there are any secrets at this point."

Much has been made of the notion that Dallas somehow is jinxed when it has to wear its blue uniforms. If Vermeil was trying to create a distraction by putting his Eagles in white, thus forcing the Cowboys into blue, he has succeeded. Dallas has tired of answering questions about something that will be forgotten with the opening kickoff.

The weather could be a more important factor. The forecast calls for a high of 15 degrees, with a strong wind. That could affect the Cowboys' superior-skill players.

"We'll be okay as long as the field conditions hold up," Landry said. "The weather always has to be considered. Usually, it causes some funny bounces. We just have to hope those bounces go our way."