There are various websites, such as Baugher's
http://home.att.net/~jbaugher/usafserials.html
But the bible for B-17 ID is Freeman & Osborne's 'The B-17 Flying Fortress Story'. All 12,731 B-17s listed with #, Delivery Location, Group,
Squadron, crash location, scrap location etc. You might find a copy on amazon. Also, Wallace Foreman's 'B-17 Nose Art Directory' lists over 8,000 ships with some # and group info.
Steve G