Right,
The B models were off the shelf 337's with no mods except replacing the baggage door with a speaker for broadcasting propaganda, and a leaflet dispenser in the front right belly.
The O2-A had a third spar in the wing, and hard points, 2 in each wing. The elevator was the longer chord from the 336 model, giving the O2-A a heavier elevator control as preferred by military pilots. One of the main drawbacks of the O2 was it had side by side seating, not tandem.The windows in the door and just in front allowed the pilot to see the ground from the left seat. Otherwise he'd have to turn left to see, and predictability in combat is deadly. There is also a window above the pilot's head. O2-A's starting in 1968 had a larger pilot's window which slightly bubbled out at the top. This cost about 2 kts in airspeed, but made visibility much better. Look just above my head, in the earlir production O2's the window would have stopped below my nose. Also if you look carefully at the rear windows, there are little doors in them. These allowed observers to fire M-16's out the windows.
Try www.cessnawarbirds.com for more info.
Some O2-A's also had skids of titanium installed on the belly to assist in gear-up landings. The black strip on the belly.
