AS to the pick-up coils; 285/385 is just right.
But they are polarity sensitive. SBM units are different from /6 &440 which distributor shafts rotate in reverse to SBMs. And Lean-burn models may also be different from non-lean-burn; not sure.
They are color-coded. IIRC SBMs have a black and an orange wire. And;Counter-rotating have a black and I think a gray. Do not swap them.
Put a timing light on your engine and observe the advance marks at idle. Then slowly rev it up; the advance mech should slowly, progressively advance the marks steadily on the way to about 3600 rpm. There should not be any jumping around, dropped sparks, or multiple sparks in the wrong place from those that went before. This proves the polarity is probably correct.
That pick-up coil is a signal generator, and you can test it. Disconnect the D from everything and pull it out of the engine. Hook it to an analog ohmmeter , set to indicating very small voltage, then slowly spin the driveshaft while observing the needle. You should see a steady blip on the needle to about 1/2 volt, or more. If it is erratic, spin the other way. Make sure the spin direction that it works properly, matches the spin direction of the engine.
These devices generally work for decades and decades and fail catastrophically if they do.
As to the ECUs , any ECU will work on ANY engine, some better or worse than others; but, they don't care how many cylinders it is firing. They only care about receiving the electrical pulse from the pick up. And of course power in, and case ground back to the battery.
The source of an intermittent miss, in order of most likely, usually is; a fuel contamination issue, an AFR issue, or a valve sealing issue. Sometimes an over-advanced ignition timing issue.
Sooty plugs may be manifesting the miss, but the ultimate source of that goes back to one of the aforementioned; don't be fooled.
Plug-gaps go with the coil; crap coils use tight gaps, hi-powered coils can use more gap. Generally, a gap of .035 is doable,and sufficient.