No spark...

Ok that is a Second generation 4-pin ECU, and the ballast is for the coil. It works in the exact same wiring harness, so long as the ballast connector has not been modified.
>To test the ballast; simply bypass it with a straight battery voltage to the coil +; It will handle this for testing purposes.
>To test the ECU, simply pull out the coil wire from the D-cap, and near-ground it. Then every time you turn the ignition key to "off", from "run", the Ecu should spark the coil one time.
> to test the pick-up, the reluctor gap ought to be in the range of .008 to .011, but I have seen engines running on anywhere from zero to .030. Then, again pull the center coil tower-wire out of the cap and near ground it. With the key on, and in "crank mode", there should be a stream of sparks jumping the gap.
You can even do this with the distributor out of the engine and laying on the fender, it does not need to be grounded, just spin the driveshaft in the normal direction, and watch for the sparks at the near-grounded coil wire.
> the Pick-Up coil is directional. there are, to my knowledge, at least three different pick-ups, one for CW rotating, one for CCW rotating and one for the early computerized system. Any one of them will spark in either direction, but if the wrong one is installed, the engine will not rev up properly.
The identifiers are the colors of the wires., they come in IIRC, orange, violet, and black. For a SBM you need the Orange one.
They all have the same coil resistance which is just a lil north of 300 ohms, IIRC.
>to check the power supply to the Ballast, take the supply wire off and plug a halogen headlight bulb in there and ground the other side of the bulb back to the battery negative. If the bulb shines brightly and nothing smokes under the dash, then change the ground wire to the engine block, if it still shines bright; then yur good to go. Watch-out!, the Halogen bulb gets very hot very fast and it does not like fingerprints, often burning out prematurely. The point is to not allow the bulb to set your car on fire.

BTW
When you measure the voltage at the coil negative, you have to disconnect the negative wire off the terminal, else it will be connected to the ECU transistor, and read wrong, for purposes of testing the coil.
With the coil out of circuit, the voltage at the negative will be a little lower than at the positive, the difference going to heating the internal transformer. The longer the voltage is applied, the hotter the coil will get and the lower the voltage at the coil negative will read. Eventually the coil-temp will stabilize, and so will the voltage drop.
AND
If you measure the voltage-drop thru the ballast, with the engine running, yur gonna find the voltage going into the resistor, to be whatever the alternator is sending, whereas the output will drop to 8 volts or less over time as the ballast heats up with the load applied. this is normal.
The coil gets full voltage during cranking and whenever the ballast is cold. This gives your cold engine some 60% more spark power to help light it off. But as the engine warms up, it is fine with 8 to nine volts, low-compression engines can get away with even less. I've seen a performance engine running just fine on 7 or even less volts. so don't sweat what you see, unless it's less than about 7 volts, in "run mode", on a hot ballast.

BTW-2
With the firewall-mounted resistor, use only a Mopar designated coil, which has no internal resistor. Do not use an off-Mopar coil, which may have internal resistors. The coils are usually marked something like;
"not for use with an external resistor" or
"use with external resistor"
If it's not marked, you'll have to figure it out. which is not hard. Just pull a few amps thru it and see how low, and how fast, the voltage drops. If it drops below 9 volts, (I'm guessing) then the coil has an internal resistor, doing the job of your firewall-mounted resistor, so either bypass your ballast or get a proper Mopar Coil.
Butum if the voltage-drop remains small, I'm guessing less than a half a volt, then she's ready to use on your Ballast-resistored car.