Veterans of Ronald Reagan's Justice Department are being increasingly mentioned for two key vacancies under Atty. Gen. Alberto Gonzales. James Byrnes, chief judge of the Board of Land Appeals and a member of the Philadephia Society, could fill the slot as assistant attorney general for the environment. Roger Marzullo, also a member of the Philadelphia Society, who held the environmental portfolio under Atty. Gen. Edwin Meese, is considered a prospect for deputy attorney general.