My new 1984 GSL-SE

[rx4ur7]

System checker is Mazda's OBD reader of the time. I do not know if any of the new readers have the adaptor to fit that early a system.
Really do not know if you can pull the codes without it. Got mine from Mazda back then. Do not know if they are still available, Call Ray.
Not likely on an ECU, I have never had to replace one on a SA/FB. One, someone putting a stereo in the car and crossed a couple of wires.
First go through check all basics. Got compression? fuel? spark? clear exhaust? GCFSE?
-Check all grounds and condition of battery cables and main wires. - 1
-Check water temp sensor and connector, I have seen a few where the harness and insulation looks good but the wires were broken. Test for continuity to ecu. -3
-Down load FSM from one of the download sites.
-other possibles
-bad vacumn leak - 2
-vent switch solenoid pack
-BAV
-TPS
-MAS
BTW - Nice find looks like everything is there and original, it will make it a lot easier to diagnosis.