Really interesting story and I had never heard of it!
https://ww2aircraft.net/forum/threads/boeing-b-17e-flying-fortress-the-dreamboat-nose.43506/
"One of the 8th Air Force’s engineering officers, Maj. Robert J. Reed, was given the task of solving the problems, and in a few months he came up with a long list of suggested improvements for the B-17. The changes were beyond the capability of the U.S. depots in England to make, so the 8th Bomber Command gave Major Reed a B-17E and sent him back to Wright Field, Ohio, to make the modifications.
Major Reed’s changes were radical, especially in armament. He took the nose and tail power-operated turrets from a B-24 Liberator and mounted them on the B-17, where they provided much more firepower and better armor protection. The tail turret had a field of fire about six times greater than the original B-17 turret."
A few more pics from around the web:
Reed's configuration was considered as a YB-40 (I) model.