There's no PCM. As I said earlier I put this battery in my truck (1985 F250).
My main purpose in sharing this experience here is that reversing the polarity of a battery is a real thing no matter the specific vehicle.
There are bad things that can happen if that's done and the battery is then installed or used in a vehicle afterward.

 

Oops I say, oops

 

Got the battery fully discharged again a couple days ago. Put it back on charge (the right way this time) and as of this morning it looks to be back to normal.