The B-17 could typically carry between 4,500 lb (2,000 kg) and 8,000 lb (3,600 kg) pounds of bombs, depending on the range of the mission. This was less than several other contemporary bombers, but the B-17 was a legend more for its ruggedness.
B-17s were designed and built by Boeing, but also built by Lockheed and Douglas. This aircraft was built by the latter, not far from here in Long Beach, California. Notice the zippered slats to keep out some of the cold air while allowing the guns to pivot vertically.
Although the A-26 and B-25 look similar (outside of the different tail design), one of the museum's docents told me they fly very differently. The B-25 is fairly docile aircraft, while the A-26 is more of a beast and far more challenging to fly.