GM tried to build a long-range fighter that used parts of the P-40, A-24 and
F4U. The V-3420 was a 24-cylinder engine created by coupling two V-1710 engines;
it was installed behind the cockpit, and drove contra-rotating propellers in
the nose via an extension shaft. The P-75 was a qualified success, after a lot
of redesign. Performance was disappointing, however, and better escort aircraft
were already in service. 14 built.