Great photo you posted of one of the four original YO-58 aircraft at the 1941 La. Manueavers with the white cross on the fuselage. The YO-58 had the narrow fuselage of the Tandem Trainer before it was widened to become the O-58 series aircraft. Here are a few more historical photos but virtually no interior shots exist of the 20 O-58A aircraft .
The Original 20 O-58A aircraft had Learadios mounted on the left window sill and came from the factory with a single front throttle, no rear throttle. The fuselage frame is different than the later O-58B and L-3C. Some O-58A aircraft were modified in service by the addition of the 2nd throttle which required relocating the radios to the left wing root.
This first photo below is of the four original YO-58 aircraft, note the exposed aileron hinge coming out of the top of the wing, the O-58A had a single torque tube push rod exiting from the bottom of the bellcrank.


