Following up with my stock stereo removal experience...
First, most of my research indicated that in order to remove the stock stereo, one would need to remove a single screw that requires significant bodily contortions in order to get access to it. Definitely now what I encountered. The stock Clarion on the '85 ST has two screws. One directly above the ash tray, and another directly above the cigarette lighter. The one above the ash tray is easy to remove if you just use a small ratchet wrench with a Phillips bit. The other screw requires removal of the cigarette lighter and you can remove it with a long(ish) screwdriver. Stereo slides right out.
Interestingly, the stereo in my pickup has a "REFURBISHED" sticker on it. Wondering if that came from the dealer that way or...????
I had no idea this would be this easy. Now i'm going to have to get online and order a stereo and speakers. Planning on replacing the two that are in the floor, and adding two in the back...location TBD. I'm not interested in free-standing speakers in a box. Probably will use the location of the jump seats, since the previous owner did away with them. I'm liking the idea of the Retro Manufacturing option as shown in this Nissan 720 conversion.