There was a time when concept cars at an auto show were just that – concept only. It was rare when even a hint of the concept car ever made it into actual production.

Today, it’s different. It is too expensive for auto manufacturers to build a concept car just for show. There has to be a reason to have designers spend the time and money to build a concept car.

And while these shiny show cars are still called concept or show cars, many, if not most, eventually will become production cars. Three years ago, Plymouth introduced the Prowler concept car at the North American International Auto Show in Detroit.

This year, at the Greater Los Angeles Auto Show, Plymouth displayed a revised version of the Prowler and announced that it would go into production and would be on sale in a year.

The Prowler is a retro hot rod. It looks like a modified 1930s model vehicle that was transformed into a hot rod in the 1950s. It’s a two-seat roadster with a sinister-looking cut-down top.

The big difference is that it has all the safety features of a new car. It has dual air bags and side-impact protection. Chrysler will use the 3.5-liter V-6 engine from the LH sedans as the Prowler power plant.

The front-drive Autostick transaxle moves to the rear to make it a rear-wheel-drive car. The Prowler also will have a new-car warranty. It will be built alongside the Dodge Viper at the new Conner Avenue plant in the Detroit area. While Chrysler expects to build and sell only about 3,000 Prowlers each year, the car will do more than just highlight the Plymouth lineup.

Plymouth needs an image boost; in recent years sales of one of America’s oldest marques have been slipping. The Prowler should provide that boost. The Prowler also is expected to help Chrysler Corp. with its development of advanced materials and production techniques. Building only a few thousand Prowlers using aluminum, plastics and composite materials poses only a small risk if an unforeseen problem develops.

It allows the company to work out the kinks of using new materials before committing it to a run of 100,000 vehicles. With an expected price of $35,000, Chrysler says it will make money on each Prowler.

Let’s take a look at some of the concept vehicles on display at the Greater Los Angeles Auto Show and see if there is a production line in their future. The Audi TT is a two-door, four-seat coupe that incorporates a large amount of lightweight aluminum in its design and construction.

In fact, the hood, doors, rear deck lid and front fenders are made of aluminum. Inside, polished aluminum is used as trim for a high-tech finish. “It’s an enthusiast’s car with great charisma,” said Herbert Dremel, chairman of Audi. The TT stands for Tourist Trophy, a name associated more with motorcycle racing than auto racing.

Power is supplied by a turbocharged 1.8-liter, four-cylinder engine rated at 150 horsepower. The Audi TT was designed at Audi facilities in Ingolstadt, Germany. The design team finalized the basic concept of the TT in just one week. The prototype was completed in seven months. The TT could be on sale as a 1998 model.

Mercedes-Benz unveiled its All Activity Vehicle concept vehicle. This unique sport/utility vehicle will be built at the new M-B plant in Vance, Ala., and is scheduled to go on sale in the fall of 1997 as a 1998 model.

The AAV has a muscular, off-road look but is designed to provide a luxury ride and luxury interior as Mercedes-Benz buyers would expect. Early speculation is the price of the U.S.-built AAV will be in the mid-$30,000 range.

The concept vehicle was painted in a tasteful green-on-green color scheme and even had the Mercedes three-pointed star logo as the tread on the huge off-road tires. Crowd reaction at the show was mixed.

Most people loved the AAV and wanted to know how soon they could buy one. Some hard-core off-roaders said it was too luxurious to be a real off-road vehicle.

If you like the look of the stylish French cars of the 1930s, you will like the Chrysler Atlantic concept vehicle. It takes its styling cues from the famous French coach builders with long, flowing front fenders and elegant body style. Under that long hood is a 4-liter, straight-eight-cylinder engine that delivers 325 horsepower.

The wheels and tires are huge; the wheels are 21 inches in diameter in front and 22 inches in the rear. By comparison, most cars on the road today have 15-inch-diameter wheels.

Mazda first showed its Mazda SU-V sport/utility vehicle at the Tokyo Motor Show in October. It made its North American debut at the Los Aneles Auto Show. The minisport/utility vehicle is based on the chassis of a minipickup truck that is sold only in Japan. The SU-V is powered by a 2.5-liter, four-cylinder engine that delivers 135 horsepower.

The designers at Mazda have addressed the problem of what to do with the big, bulky spare tire; they have built a mini-Continental kit in the rear door to house the spare. The storage area keeps it out of the weather and away from thieves.

They also designed a clever fold-up step in the rear area that makes it easy to step up and load the roof rack. I had a chance to drive a right-hand-drive version of this concept vehicle last year and found it roomy and fun to drive. Mazda is gauging public reaction to this vehicle and, if the interest is there, it will most likely build it and sell it in America.