Fiat Chrysler Automobiles U.S., formerly Chrysler Group, posted a $2.58 billion first-quarter net profit that was boosted by a one-time change in its tax status. The company, now part of Fiat Chrysler Automobiles N.V., gained $2.3 billion from the tax change. It lost $690 million a year ago due largely to payment of debts to a union health care trust. …