Cool, glad to hear that it was useful. Funny how stuff like this can drift off into oblivion until one day someone stumbles across it and uses the info in it to their advantage. That right there is Pure Internet Gold.
I know the vehicle this was in is not an A body, and this post was a few years old, but I hope everyone can look past that for the sake of adding a little more information about the elusive A999 and its applications.
The 999 was used in 80s Jeeps for sure but bolting a mail Jeep trans into Jimbob's Duster is not a straightforward proposition. Correct me if I'm wrong but the Jeep 258 specific bell housing is not going to bolt into any V8 A body.
Rebuilding the trans to get the truck running is one thing but building it to run in an Abody street machine is an entirely different idea. To retrofit the Jeep unit into an A Body car, you'd likely wind up just taking all the usable pieces out and installing them into a regular 904 case.
You'd really have to verify if those particular parts match up to the car stuff though, one could very easily run into a situation requiring parts that don't exist. Like I mentioned early in the thread, matching particular parts together to try and build one of these units from scratch or from a non-original application can be tricky and perhaps not even possible without custom machining capability.