Not only pressurization problems, but the B-32 also had a history of landing gear collapses that plagued the training program at Fort Worth AAF. Quality control was not good on the early aircraft, either. Many of the problems were worked out sufficiently (including abandoning the pressurization) and a few did see combat just at the end of the war.
On the subject of the Manhattan Project, notice in Martin's photo of the TB-32 how the bomb bays were laid out with the central keel beam and bulkhead between bays, just like the '24. The uranium bomb might have fit, though I think it was too long, but the plutonium device doesn't look like it would have been an option without MAJOR structural modifications.
Here are a couple more photos. The first is one of the combat test airplanes (42-108530) after the end of hostilities:
This is "The Lady Is Fresh" in the SWPA.
This is the second production airplane on the day it was delivered to the AAF at Fort Worth. Nose gear collapse started this mess--it's not hard to see who designed the airframe is it?
Matt Gunsch has an informative thread in the Modellers Gallery/Forum of his B-32 construction in 1/72nd scale.
Scott