The idle Carrozzeria Bertone manufacturing site, where Sergio Marchionne plans to make vehicles for Chrysler Group LLC and Fiat SpA (FIATY), has a history of helping to put iconic cars on the road. Marchionne is probably hoping that some of its past magic rubs off on his efforts.

Located a few kilometers from Fiat's head offices, the site used to belong to Bertone, a prominent name in car design and niche manufacturing until its demise last year. Founded in 1912, Bertone made its mark in the 1960s when it worked on cars such as the Ferrari 250 GT, the Alfa Romeo Giulietta and the Lamborghini Miura.

Now, with Fiat completing its purchase of the site Thursday, proud and fiercely loyal unionized workers remain apprehensive about the Italian group's plans for them. Fiat's success with Bertone will be critical to both the future of Fiat and Chrysler.

Marchionne, the chief executive of Chrysler and Fiat, intends to invest EUR150 million ($218.3 million) in the plant over the next three years to transform it into a niche producer of vehicles. Chrysler products made in Turin will be shipped throughout Europe and imported into North America.

Chrysler will end its production partnership with Magna International Inc. (MGA), which is the sole manufacturer of Chrysler models on the European continent. Magna assembles the Chrysler 300C sedan and Jeep Grand Cherokee. That work would be moved to Bertone.

Chrysler's long-term survival rests with what Marchionne will do to expand the auto maker's international sales. The company relies on the North America market for about 90% of its sales. That market has been rocked over the past year by an economic recession.

The story of Chrysler's future Italian manufacturing home could be a chapter taken from the auto-making history in the U.S.

Bertone's site, encompassing four buildings and employing 1,140 workers, was once a hub of activity with the capacity to produce 70,000 vehicles a year. Then, after the death owner Giuseppe Bertone in 1997, the plant ran into financial difficulties and eventually went idle starting in September 2006.

The site fell victim to an industry trend that saw major car makers bring in-house the production of limited series of their models such as convertibles. The last model to roll off the Bertone line was BMW AG's Mini Cooper, for which Bertone did the paintwork. The Bertone plant went into special administration two years later.

To draw attention to the plant's problems, a small group of workers lived in a camper van parked outside the factory for more than a year in 2007.

Bertone's widow, Lilli, stopped by the camper once and handed the workers a tray of home-made cookies.

"She said 'I am with you. I am like your mother. Hold on tight'," said Massimo Gazzitano, a worker at Bertone for 30 years. "We still have those cookies; we wanted to give them back to her."

Last August, Fiat bought the site at auction, keeping Bertone from liquidating.

"We achieved an important result. Bertone didn't go bankrupt, even though it was a close call for some time. But I am waiting for Fiat to tell us what will happen now, so I am still worried," said Rocco Vallone, who joined his father and uncle at Bertone in 1977, when he was 18.

Lino La Mendola, a representative of the union, Fiom, said it is essential that the workers keep their acquired rights in terms of salary and ranking.

With the sale officially completed Thursday, the union may not have long to wait to hear what Marchionne intends to do.

-By Milena Vercellino, contributing to Dow Jones Newswires; giles.castonguay@dowjones.com

(Jeff Bennett in Chicago and Gilles Castonguay in Milan contributed to this article.)