New documentary shows progress at Stellantis Mack Assembly Plant in Detroit ‘We did work to ensure that Detroiters saw Stellantis as a company of its word’ Updated: July 29, 2021 12:48 am New documentary shows progress at Stellantis Mack assembly plant DETROIT – When Stellantis merged with Fiat Chrysler, it didn’t waiver on the deal with the city of Detroit to revitalize not only the Mack Assembly Plant but the surrounding area. Local 4 has followed the plant’s revitalization for the past few years. From the 2019 job fairs for Detroiters to the approval of the tax incentives, new construction and revitalization of the east side neighborhood around the plant.