4 & 5 pin ECUs

Maybe this:

The 4 pin resistor is not "a" resistor, it is TWO resistors "in one box". IF the factory wiring connectors are undamaged, they have locating pins which prevent incorrect connections. that is what the "U" cutout is at one end, not only an "index" for us not using factory connectors, but the factory connector fits into that "U"

So simply, there are TWO different resistor values, one for the coil and one for the "box."

The resistor and wiring connecting to the coil, and to the key, IS UNCHANGED from the old points system. IN FACT if you were to "go dead" on the road, you could slap in a breaker point dist, hook the dist wire to the coil NEG, and pull the connector out of "the box" and be on your way