I need some help to I.d. my differential. Its got 10 bolt pattern on the cover and a clamshell cutout on each side halfway down. Its stamped on the backside passengers side 9783393 and right above that is J286. Julian date? On the opposite side in the same spot is an A. I think its open or a blown posi as when I jacked up the rear end the tires spun in opposite directions. Heres a photo that was very hard to get in my tiny garage.

 

Sorry the photos a lil upside down as I was!

 

Its in an all original 67 442 automatic. Thats a pontiac rear end isnt it?