Any car can be a convertible -- for a price

In today's economy the consumer is often warned about the great put-on, but now an eye of caution also needs to be directed toward a new ''put-down,'' the conversion of standard automobiles into convertibles.

Even though Detroit carmakers now are taking a new look at the ragtop, with Chrysler, Ford, and Buick already on the market with a convertible, the conversion firms continue to do their thing.

The cost of conversion starts at about $2,000 and, depending on the other customizing work required, can skyrocket to as much as $50,000.

In the late 1970s the convertible became a collector's item, and exorbitant price tags were attached to used factory-produced ragtops.

As a result some innovative firms concluded that a new market for the convertible had emerged. Chop off the top of a production automobile, add some mechanisms and cosmetics, and a sporty convertible could emerge from anything shipped out of Detroit, West Germany, or Japan.

Although most owners are, in fact, satisfied with their converted chassis, there are a number of things to keep in mind about converting a car into a convertible.

The major consideration should be safety. When you whip off the top of the car, has safety been sliced away as well?

Structural integrity can be sacrificed in the conversion process. How the changes will affect the security of the occupants of the car must be analyzed as rigidly as price, workmanship, and style.

Some change in overall automobile weight can be expected, and this usually affects the road behavior of the vehicle. The driver should understand the weight difference and modify his driving techniques as well.

The body style of some cars make them more susceptible to structural impairment during conversion. It's important to find out just how much structural damage a particular model will suffer from the conversion surgery. Conversion of some models is complicated and may take weeks.

Ritzy convertibles became classic when the last roofless Cadillac Eldorado rolled off the production line in 1976. General Motors blamed a lack of demand for the ragtop's demise, but demand is apparently growing - and even the Detroit manufacturers are looking hard at the ragtop once more.

Some firms are new to the conversion field, while others have many years of experience. If you're in the market for a ragtop and can't wait for more of them to emerge from Detroit, research the conversion companies to determine their respective track records.

Structural rigidity is a standard of reputable firms converting cars into convertibles.

Workmanship, of course, must be first-rate. Warranty policies differ between companies and should be scrutinized carefully.

Some manufacturers specialize. Auto Graphic Design in Costa Mesa, Calif., converts the Mercedes-Benz. Guiliano Motors Ltd. of Philadelphia modifies the Datsun 300CD and 280CE. Others, like Coachbuilders Ltd. in Fort Lauderdale, Fla. , convert a variety of cars.

Coachbuilders yearly production of about 1,000 convertibles includes the Cadillac Eldorado, Buick Riviera and Regal, Chevrolet Monte Carlo, Oldsmobile Toronado and Cutlass, Pontiac Grand Prix, Lincoln Mark VI, and the Ford Mustang.

The imaginative entrepreneurs were right. Convertible conversions are big business.