Are EEC modules engine specific?

My old 1987 LX 5.0 had an EEC that had a sticker on the bottom( or was it side? Long time ago...pushing 7 years now) that said "for v6 taurus 3.0 only" (or something to that effect) when I pulled it out to trace some wires. I had no operational concerns and the car ran 100% so from this I could conclude:
1. There are all interchangable (doubt it)
2. Someone took the time and trouble to attach this apparently meaningless sticker to the underside of my EEC and then slip it back under the kick panel, bolt it up and put some old looking dust on top
3. Taurus eec and mustang eecs are the same.
4. Somebody knows something about EEC-IV's that I dont and put that in there.

I bet some of them do interchange but wouldnt it need different maps for different engine airflow characteristics? I think the v-8 are "a9l" so look for that code somewhere on the unit.

They're neat little intel 15 mhz chips in there (so I'm told...cutting edge in 1986/87). I wonder if they have eprom or something that could be tweaked.

edit: I just looked at the other thread and it looks like #2 is the winner! No way the 2 could swap and still have run my 5.0