Lockheed was building B-17's at the Burbank plant, if memory serves correct. They even built a prototype with four Allison engines. It was fast, and had range. An electrical fire destroyed it, again, if memory serves correct.
The really odd thing is that Consolidated Vultee in Nashville was the second source for the P-38. See the problem? An aircraft company geared towards large aircraft was told to produce P-38's, the most difficult plane to build in World War II, while the company that designed the P-38 was told to build B-17's. Consolidated never got the hang of building P-38's, they took years to build 113. Imagine what would have happened had common sense prevailed, and Consolidated had been tasked with building the B-17's Lockheed was told to build, and Lockheed had been allowed to devote the B-17 lines to production of P-38's.