I had learned that a P-38G-5-LO with s/n 42-12866 was directly connected to the XP-49 program. This P-38G aircraft was modified to serve as a testbed for an experimental gun installation consisting of two 20 mm cannons and four 0.50-cal machine guns. As you can see in the photo, the 20 mm cannons were mounted diagonally. This armament configuration was tested and validated for the XP-49.
So if the XP-49 is implemented in the game, then the guns in the nose would definitely be like this.