DETROIT (Reuters) - The head of Fiat SpA said on Monday that the company's top-performing U.S. dealers will get the first tranche of Alfa Romeo vehicles when the sporty Italian brand is reintroduced to the U.S. market this spring. Speaking at the Detroit auto show, Chief Executive Sergio Marchionne said a second Alfa model will come to the United States in 2015 but he did not say which one. The first model scheduled to appear in Fiat showrooms - the 4C - will be the first Alfa Romeo to be sold in the United States in nearly two decades. (Reporting by Bernie Woodall; editing by Matthew Lewis)