To answer both Framer's question and a bit on the B-32:

The reason the US continued to build two types of many aircraft was due to the way their war production programs were set up. Aircraft manufacturers were often tasked with designing an aircraft to meet some military requirement. The US Army or Navy usually chose the best two prototypes for further development or contracted those two into production.
This was done to ensure that if there were problems with one design or the other in going from prototype to production (often the case....just look at the Germans for examples of this with single production line aircraft) then the most successful design could be pushed ahead while there was still a second design following, just in case.
This was the case with the B-32. Consolidated was tasked along with Boeing to design and build a super heavy bomber with a pressurized cabin, remotely controlled defensive systems, etc. Boeing's design was the B-29. Consolidated ran into all sorts of problems with their design so Boeing got the major production go ahead while Consolidated's B-32 was scaled back, simplified, but kept in limited production....just in case. All told, Consolidated made made just over 100 B-32's most of which were used as reconnissance aircraft.