dsc19440.jpg

Overall view facing forward, taken from the tail of the plane.

Near the top can be seen the control cables, from the opposite vantage point as compared to dsc19370.jpg.

Forward of the cargo door are the two emergency exit windows (they're dimmer and greener than the wide windows farther forward).

Just forward of the emergency exits at the top of the plane is a storage compartment (the door is painted green and labeled "center wing access"). Just aft of this storage compartment (about as far forward as those emergency exits) is the location of the cut-out for the top turret. Since the emergency exits (highlighted by the yellow markings on the outside of the plane) are behind or at the rear of the bomb bay, this means that the top turret was also behind the bomb, rather than immediately behind the cockpit as in later versions of the plan.

I was able to find one picture of an LB-30 with its top turret aft of the bomb bay.