True but it was a test bed that was before things were ready. Under powered and to slow to do the bombing job. But pushed the limits of the day. Soon after much more powerful engines would be introduced that would solve much of its problems. The B-36 was the true result of the B-19.
Since we've already stretched WWII, let me ask you to consider the amazingly sleek Ambrosini Sagittario, an Italian aerodynamic research aircraft based on the Ambrosini SAI.7, an Italian racer flown before World War II which entered production as a military fighter/trainer.
In the early '50s the metal fuselage was fitted with wooden 45 degree swept wings and tail and a Turbomeca Marboré turbojet installed with the exhaust was routed out the bottom of the fuselage. The tail wheel was retained, so special shielding was added to protect it from the engine exhaust.
The later all metal Aerfer Sagittario 2 differed in having a tricycle undercarriage and rather ugly fully transparent cockpit glazing, exceeding Mach 1 in a dive, the first Italian craft to do so.