For the Boston Celtics, the transformation became official tonight. In a year, they have retooled themselves on th fly from being a fancy-passing, finesse team into a gang that can bash and elbow with the best. The men who have both changed and supercharged the new Colts -- 7-foot Robert Parish and 6-foot-10 rookie sub Kevin McHale -- announced the new Boston style to Philadelphia. r

In delirious Boston Garden, the storming Celtics won their 13th straight game, and their 25th in 26, as they held the mightily muscled Sixers at arm's length for a 104-101 victory, despite 35 points by the sublime Julius Erving.

The victory was not assured until Parish made two foul shots with nine seconds remaining and Sixer guard Andrew Toney bobbled the ball away under double-team pressure before he could try a game-tying three-point shot as time expired.

For the Celtics, the win was doubly emphatic since it capped their season-long pursuit of the Sixers. Boston now leads in the standings by 12 percentage points and by one in the lost column: 43-9 to 44-10. Never in NBA history have two teams in the same division (Atlantic) had such spectacular records, and not since '72 have two clubs in the entire league won at such a withering pace in the same season.

This game was not simply a test of skills, but of will. Last year in the playoffs, Boston was bruised and intimidated by the shot-blocking, elbow-wielding menaces from Philadelphia.

With the retirement of Dave Cowens this season, the Celtics were supposed to have an identity crisis. Instead, they found both a new personality, perhaps an even better one.

"Now, we can force the ball down people's throat," said Boston guard Chris Ford, grinning. "In fact, we can even shove it down Philly's throat occasionally. Now, we've got shot-blockers, too. And people who can score inside. We could make all the great passes and 20-foot jumpers we wanted last year, but if you can't fight on even terms under the glass, you haven't got much margin for error."

This evening, the Celtics outrebounded Philadelphia, 46-38, and had more blocked shots, 6-4. Though this game was always close, Boston never leading by more than seven points, the Celtics still were in control throughout; the Sixers had a pair of two-point leads, three one-point leads and that was all. It was usually the visitors struggling to stay close.

Though the Celts led throughout the last 15 minutes, Erving engineered one glorious rush as he scored 10 consecutive Sixer points to cut what had been a 90-83 Boston lead to 100-99. "It looks like the Doctor was alone in the gym," said Boston Coach Bill Fitch.

That is when Parish showed up. The big man who has been Fitch's reclamation project -- and who has just made the NBA All-Star team for the first time -- blocked a Dr. J drive. Seconds later, he drove and shoveled an assist to Cornbread Maxwell for a dunk. Twice more, Erving took the whole show in his hands, as he had at almost every crucial juncture. And twice more he missed, only to see Parish above the iron grabbing leather.

The Sixers got a bank-shot follow-up from Bobby Jones to cut their deficit to 102-101 with 16 seconds left, then fouled Parish at midcourt, hoping that the tallest Celtic would prove a nervous foul shooter with so much at stake. A high arc, a soft touch and a little body English was all Parish needed.

If Parish, with 21 points and game high dozen rebounds was big poison, then McHale was little poison. It is Philly that has the marvelous bench -- The Pine Boys. But sub McHale proved a perfect answer to Bobby Jones tonight, mirroring the super sixth man's 14 points and six rebounds with 13 points and five rebounds of his own.

The old Celtic gifts were present too: Larry Bird's 24 points, Tiny Archibald's 10 assists and 18 points, and Maxwell's 18 garbage points underneath. But it was the new Celtic duo that had the Good Doctor making a diagnosis. "They still need another guard," said Erving. "And this just evens the series (Philadelphia won an early season game at home in overtime) but I have to admit that they're different now. They've got guys down in the hole with us. Parish and McHale are doing a whole lot of things that we're not countering yet."

A glorious resumption of a very old war has begun.