Can anyone help identify transmission?

Most definitely an A999. Mine is from a 1989 Dodge Diplomat that I found chucked into the back of an old panel van in a salvage yard.
These are damned good transmissions. Stronger than the A904, then you got the 2.74/1.54 1st/2nd gears and then lock-up. Which reduces your RPM's by 150-200 when cruising on the highway/freeway.
I rebuilt mine with a premium rebuild kit using kevlar bands, Kolene steels and Red Eagle clutches.

I went silly with mine and took out the lock-up function & installed a Turbo-Action Cheetah stage 2 Non-LU valvebody. I kinda regret it but oh well, not a big thing with me as it's now much stronger than it was when it left the factory..