GARY STEVENSON has been named President/Marketing & Media Group of NBA Properties, the marketing arm of the NBA. He will be responsible for all NBA marketing activities, including the NBA, USA Basketball, and the WNBA (NBA)....TOM CHESTNUT resigned as 76ers Exec VP. Chestnut was hired as COO in July '95 (76ers). His duties diminished with the "more hands-on style" of leadership of new team President PAT CROCE (PHILA. INQUIRER, 8/17).