That's interesting Gadge. Did the front/rear 337 have Lycoming horizontally opposed four engines?
Nope; a pair of Continental IO-360 fuel injected 360ci flat sixes, with McCauley constant-speed props.
[BTW, I've seen a crankcase set of a Lyc O-720 flat 8 in the metal; crikey, what a monster!]
The O-2 had armament mounting hardpoints, too;
Armament
Guns: SUU-11/A Minigun Pod
Hardpoints: Four MAU-3A bomb racks
Rockets: LAU-59/A Rocket Launcher, MA-2/A Rocket Launcher
Bombs: SUU-14/A Bomblet Dispenser