Paul Abramowitz admits he hasn't slept much lately.

As president of Western Costume Co., he's supervising the move of its entire stock of costumes and props--about 3 1/2 million of them--from Hollywood to North Hollywood.

The move, expected to take 28 days, started last week.

"How do you move all of this and still do business at the same time?" Abramowitz asked recently as he walked through the 65-year-old structure on Melrose Avenue that Western is vacating so Paramount Studios, which owns the site, can put up an office building.

"It's probably the largest collection of vintage clothing in the world, and it has to be preserved," he said. "Most of the clothes are genuines."

That morning, he had spotted, among the packed boxes of more than 3,000 swords, two authentic European weapons imported by Western in the 1920s for the Eric von Stroheim classic, "The Wedding March." They were pulled from the regular collection and placed for packing with the special items.

"We find those kinds of items all the time," said Abramowitz, explaining that no piece-by-piece inventory has ever been done of Western's apparel and props. "And it never will be. It would be a monumental task and too costly."

He estimates the company has at least 2 1/2 million costumes, prompting his stepson Adam, 11, to ask: "Do you know you have two costumes for everybody in the state of Maine?"

Chief costumer Bob Pecina, who has worked at Western on and off since 1945, observed: "We've started an inventory many times but never finished. But this place was always No. 1. All the biggest designers were here, Walter Plunkett, Edith Head, Adele Palmer, Irene Sharaff, Renie, Yvonne Woods, Eddie Stevens. And all the stars. My favorite was Barbara Stanwyck. She was such a lovely person. And Errol Flynn and Gilbert Roland. Gilbert is still a friend of mine."

As for props, probably a million have been acquired by Western since it was founded by Indian post trader L.L. Burns circa 1912, when cowboy star William S. Hart, complaining about the accuracy of the garb he had been given, hired him to be official supplier of Indian clothing for his pictures.

Burns' company originally was housed in downtown Los Angeles at 7th and Figueroa streets in a tiny building. Western moved several times before taking up residence in 1932 on Melrose Avenue in a former furniture warehouse. Burns lost control of Western during the Depression; the company went through several owners until Abramowitz, author Sidney Sheldon and agent Bill Haber bought the collection last year.