DEARBORN, MI – American Specialty Cars Inc. engineers thought they had a winner when they converted a Chrysler 300 4-door sedan into a convertible.

Unveiled at the North American International Auto Show in Detroit in January of 2005, ASC touted it as “a highly feasible prototype that could allow any auto maker to create the first production 4-door convertible in almost 40 years.” The last in the world was the Lincoln Continental ragtop, discontinued in 1967.

Eighteen months after the big debut, ASC still is trying to find an auto maker interested in putting such a vehicle into production.

“Dealers like it; all sorts of people like it,” says Ken Stewart, ASC’s director of business development.

So why haven’t the auto makers bitten?

“I’d like to ask them that, although ASC has been talking to several OEMs and we may be close,” says Stewart. “It would really open up the convertible market. Right now, it’s limited to 2-doors, and that turns away a lot of potential buyers.”

Adds ASC Executive Vice President Jeff Steiner: “There’s a big ‘white space’ on the entire industry’s marketing map for a car like this, and we think this type of vehicle might be just what the doctor ordered for OEMs looking for whole new emerging market segments.”

Stewart says the prototype was innovatively engineered, including the installation of a cross-car steel bulkhead just behind the car’s front seats. It is attached to new “half” B-pillars between the front and rear doors to keep the car solid, quiet and able to pass a side-impact crash test.

“It’s not just a matter of lopping off the existing roof and installing a convertible top,” says Stewart.

Costs associated with the sophisticated engineering is scaring off some auto makers.

“Believe me, we looked at the possibilities of a 4-door convertible and tried to make a business case,” says Joe Eberhardt, executive vice president-global sales, marketing and service for Chrysler Group.

“But the technology to make the body rigid enough is expensive, and it would create a price point that the customer isn’t willing to pay,” he says. “I think there’s a market for the vehicle, but it suffers because of the price point.”

Chrysler makes the Sebring convertible, a top-selling convertible in the U.S. Eberhardt says chances are “fairly slim” the auto maker will produce a 4-door convertible.

Dealer Thomas Castriota of Castriota Chevrolet in Hudson, FL, believes a stylish 4-door convertible would sell – if the price were right.

“If the price is too high, you scare away a lot of people vs. those you’d pull in by offering a 4-door,” he says.

sfinlay@wardsauto.com