Petty Enterprises has sold majority ownership to the equity firm of Boston Ventures. NASCAR’s most storied race team gives up control of an organization that has been family run since 1949 with the deal announced Wednesday. Barry Baker, managing director of Boston Ventures, will be Petty’s new chairman. David Zucker takes over as chief executive. Zucker most recently had run Midway Games, a Chicago video games producer. The partnership gives Petty the stability it needed to retain Bobby Labonte, who signed a four-year contract extension after Boston Ventures came aboard. Richard Petty says he’ll still have a large day-to-day role with the team.