According to the article that Linchuck posted there are only 8 players from the 2004 team.
Of the 25 players on Boston's World Series roster, only eight remain with the team: Manny Ramirez, David Ortiz, Curt Schilling, Mike Timlin, Jason Varitek, Tim Wakefield, Doug Mirabelli and Kevin Youkilis (who didn't get a World Series at-bat).