First of all, it might be easier for us to follow if you keep all this in one thread. That way we can go back and read the previous stuff all in one place and maybe avoid confusion and repetition.
Now. My understanding is that swapping to a newer system with obd2 can be done. BUT... It is probably more complicated by a large Margine. I don't know all the details. But around the time obd2 came on the scene, the whole wiring structure of vehicles started to change. Instead of controlling everything with switches, a few relays and maybe one microprocessor, the ECU, the various vehicle systems started getting their own microprocessors. So now, you basically have a whole bunch of tiny computers controlling different systems - the ECU for the engine, another for the transmission, another for body functions like lights and door locks (the GEM), security systems, etc. And these all communicate with each other. They also increase functionality by.making it easier to add timers and safety interlocks and other crap that most of us don't even know is there. But this changes the whole architecture of the wiring systems in the vehicle. The newer the vehicle, the more advanced it is. But this process began around that time.
So you can't just toss a young whippersnapper obd2 ECU, engine harness and engine in there and expect it to play nice with the grandpa style body wiring and instrument cluster. A lot of changes have to be made to try to make that dysfunctional family get along.
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