No spark

It is not clear to me what you have actually done for diagnostics. Replacing parts is not diagnostics, exactly. EG could be an issue in a connector, wiring harness, or possibly a wiring error/ old wiring hack

You need a multimeter, a 12V test lamp (LAMP not an LED) and a couple of alligator clip jumper leads. I mean that in general for wiring issues

With key in 'run' measure coil + to ground. It should NOT be full battery voltage, rather, quite low, varies from say 6--up to maybe 8v or a bit more. This shows the ECU is getting power, it is grounded, and is drawing current through the coil

Separate the distributor connector "Rig" a test gap (even an old plug) to the coil tower with a wire core wire. This can be a low voltage wire if you "hang" it in free air. Do NOT use the radio suppression coil wire. Take the connector end going to the engine bay harness, NOT the distributor. Tap the bare terminal of that connector to ground, with key in "run." Each time should produce a single "snap" hot spark.

Check inside the dist. Look for shaft play, rust/ debri, damage due to reluctor / pickup contact. If possible remove dist, but you can hook your meter to the dist pickup and crank the engine, with the meter set on low AC (not DC) volts. The pickup should generate about 1V AC

Now you must check while cranking. Wire your meter to the coil + and crank the engine using the key. The coil + should be about the same as battery. In other words if the battery pulls down to about 11V when cranking, then the coil + should be about the same, when cranking

The dist. pickup connector is especially prone to corrosion because there is no real current there. Pull it out, stck it in, feel for tightness. Get a light and inspect for crud.

Unscrew the lock screw at the ECU and "work" that connector in/ out and inspect it. At least one member here had a terminal failure inside that connector, and I have seen that years ago.

The ECU MUST be grounded. Unbolt, scrape around the bolt holes, and use star lock washers.