Here’s a
Link to the Robart Fowler flap hinges I mentioned.
As can be seen, they allow the surface to slide back while deflecting downward.
As to the Bird Dog, I believe the early versions had Slotted flaps that deflected 60 degrees, while later versions had Semi-Fowler flaps that deflected 40 degrees.
My reference on the L-19/0-1 does not mention a change in maximum flap extension nor a design change, except from manual to electric operation. It states :
A single, slotted Fowler high-lift flap is installed at the trailing edge of each wing. The flaps are controlled by a hand lever and cable-operated bellcrank, and push-pull tube mechanism. Most L-19's have been converted to electric flap operation, which provides any angle of flap desired from 0 degrees to 60 degrees. Maximum angle of extension is 60 degrees, with intermediate positions on the manual system of 30 and 45 degrees.
It also describes the materials used and the motor location for the electric flaps. The wing never changed on any of the L-19/0-1 variants. The conversion to electric flaps occurred around 1953 after the accident rate increased in the type. Investigations showed that most were during the landing phase when pilots were engaging flaps manually which took a free hand from the controls and made them shift position for leverage to operate the handle, which took some effort. Historically, Bird Dogs flew with manual flaps for a much shorter period than they did after the conversion to electric.
My resource is "The Lovable One-Niner", a definitive reference on the L-19/0-1.