Here is a good starting point:
http://www.305thbombgroup.com/http://www.8thafhs.org/bomber/305bg.htmThe 305th has a very active Facebook page here:
https://www.facebook.com/groups/54028564457/I highly suggest joining the Facebook page and contacting the administrator Jigs Bumper. He's extremely knowledgeable about the history of the 305th and I'm almost certain he can help you learn more about your great grandfather.
Cheers,
Zack
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Curator - EAA Aviation Museum, Oshkosh, WI
"Let No Story Go Untold!"
http://www.timelessvoices.org