NEAR 50 AND NIFTY; WITH A FASHION MAKE-OVER ... THE BEAVER BECOMES A BOY TOY.

Byline: Barbara De Witt Daily News Fashion Editor

The icons of our youth are turning 50. Sally Field of ``Gidget'' and ``The Flying Nun'' hit the mark last year. Michael Douglas, Cher, Linda Ronstadt, Barry Manilow and even Bugs Bunny have already hit the big 5-0.

But the Beaver? No way.

Oh, sure, the rest of us may get gray hair and wrinkles - but not that cute kid from ``Leave It to Beaver.'' In our hearts and on our television screens, he's forever 10.

But think about it. ``Leave It to Beaver,'' starring Jerry Mathers, first appeared in 1957. And just like other San Fernando Valley baby boomers, Mathers grew up, went to college, got married, had kids, got divorced and ate way too many burgers and fries.

Yeah, it's true. The Beaver pigged out.

After years of being a cute kid, Mathers became a chunky, middle-aged guy with a spare tire big enough for a truck (OK, a minivan).

It's not the way he wanted to turn 50. So with his June 2, 1998, birthday on the horizon, Mathers decided to lose his gut and gain some babe magnetism.

First stop was Jenny Craig, a diet center where he learned to trade T-bones for sweet-and-sour shrimp. Besides eating the specially packaged food on the program, he ate veggies and took up running.

Forty pounds lighter and with a trim 32-inch waist, Mathers was ready for a Daily News fashion makeover. With a team of stylists and a new haircut, the Beaver became a hunk in a velvet vest ... a boy toy in a black leather jacket ... a GQ kinda guy in pinstripes and French cuffs. And, by the way, the first male spokesman for Jenny Craig diet centers.

Finally, Wally has some competition.

``Wally (Tony Dow) always got the girls,'' Mathers said of the handsome kid who played his big brother. ``He was the all-American boy who everyone strived to be like ... and the funny thing was that he was actually shy, while I was really more outgoing ... but girls just thought of me as the good boy.

``Now that I'm older, it's nice that people aren't afraid to talk to me when they see me. They think of me more like a friend than an icon because they grew up seeing me in their homes.''

Fashion statement

The cherubic face, the dazzling grin and the twinkly eyes are still there, but in a V-necked red cashmere sweater, lying in a bed of leopard-print pillows, this is not Wally's kid brother. But like his TV character, he still worries about wearing a sweater without a shirt underneath.

``I'm afraid I'm more of a Levi's and polo shirt kinda guy. Do you really think this looks good on me? And what about this velvet vest and iridescent shirt? Are these velvet pants too tight? Are tie bars really back in?'' he asks.

Yes, yes, yes and yes, we tell him. Tight is good when you don't have belly overhang, and tie bars may be ugly, but they're back in fashion favor right along with cuff links, cocktails and cigars.

Between ensembles donned for his fashion layout, Mathers brings us up to speed on his life.

After ``Leave It to Beaver,'' Mathers attended Notre Dame High School in Sherman Oaks, got a degree in philosophy at UC Berkeley, worked as a loan officer for Security Pacific Bank in Woodland Hills and worked both in front of and behind the camera for a number of years.

He was back in the limelight in '85 for a series spinoff ``The New Leave It to Beaver,'' in which the Beaver and Wally were grown up. More recently, the Beav got attention with a remake of the show on the big screen.

Now he's writing a book about his life in show biz. It should be out next spring.

It began, he said, when he was 2, shopping at Desmond's in the Valley with his mother. He was asked to be a model, and he soon went from the runway to television. ``In those days,'' he said, ``they shot TV live, so they needed children who were used to performing in front of crowds.''

On the couch 

These days he's a frequent guest on Jay Leno's ``The Tonight Show,'' but mostly he travels around the world promoting ``Leave It to Beaver'' as the reruns are shown in 80 countries and translated into 40 languages.

He also speaks at colleges on the history and future of television - he believes that, within 10 years, viewers will be able to manipulate the plots of their favorite shows. He also has a catalog line of ``Leave It to Beaver'' memorabilia, including baseballs, mugs and Mayfield High School letter sweaters.

In his spare time, you'll find Mathers running to keep his new bod in shape. He admits it takes a lot of work, but with his adult-onset diabetes he takes his health more seriously than he did a few years ago. He also likes to go camping, restore antiques and work on his red Porsche. And sometimes you'll find him hanging out on ``Beatles Night'' at Borage in Calabasas.

But let's get the real scoop. Did you ever really hang out with Wally?

Laughter. ``Yes, I did,'' he said. ``In fact, when I got older and dating age, we double-dated. One of the best times was when we went to the Whisky-A-Go-Go in West Hollywood to see the Turtles perform - boy, is that dating me - but actually we liked the house band better. It was a bunch of UCLA students who later became known as the Doors.''

``Other stuff you probably don't know,'' he confides, ``is that I cry during sad movies - I'm a Gemini - I love paisley and wear white cobra cowboy boots with my Armani tuxedo.

``And I think the world needs more common sense.''

What the Beav likes

These are a few of the Beaver's favorite things:

Color: Kelly green.

Cologne: Gray Flannel.

Designers: Perry Ellis and Armani.

Scent of a woman: Tuscany and Opium.

Valley restaurant: Borage in Calabasas.

Car: Porsche.

Author: Kurt Vonnegut.

Song: ``Those Were the Days,'' by Cream.

Athlete: boxer George Foreman.

Healthy snack: raw red peppers.

Movie: ``The Wizard of Oz.''

Binge food: T-bone steaks.

Ice cream: chocolate chip.

TV show: ``3rd Rock From the Sun.''

Date: dinner and a walk along the beach at sunset.

CAPTION(S):

7 Photos, Box

Photo: (1--Cover--Color) ``Leave It to Beaver'' star Jerry Mathers goes GQ in a three-piece velveteen suit by Claiborne, $374. His tie bar, $18, and cuff links, $38, are by Yves Saint Laurent, all from Macy's Fashion Square.

(2--Color) Mathers in red cashmere sweater by Club Room, $150, from Macy's.

(3--Color) Ready for the '90s club scene, Mathers sparkles in a metallic shirt, $88, teamed with a burgundy velvet vest, $145, both by Rodriguez. His velveteen pants are by Claiborne, $98.

(4--Color) The Beav as suave sophisticate in gray pinstripes by Claiborne (jacket, $185; trousers, $72). Pocket squares have made a fashionable comeback.

(5--Color) Beaver becomes boy toy in a black leather jacket. Peacoat by Kenneth Cole, $318.75, Macy's.

(6--7) (6--Color only) Jerry Mathers, below, just before the make-over, and above, way before with Tony Dow (as Wally) in ``Leave It to Beaver.''

David R. Crane/Daily News

Box: What the Beav likes (See Text)