here's a single resistor (points setup) on '70 or '71.
View attachment 1716342917
The OP's '72 Demon looks to have the resistor mount hole above the lip. But if there is a mounting hole below, that's the better location in terms of keeping it dry.
1. Mount a new or used 0.5 Ohm resistor.
Not 5 Ohm. Not 1.5 Ohm. 0.7 Ohm is OK.
2. Disconnect points distributor at coil negative.
View attachment 1716342884
3. Install magnetic pickup distributor.
Side note: Preferably one with a Chrysler performance advance curve (non-smog). If you don't know, then best to do a quick and dirty check on the bench. Plenty of posts on FABO about identifying the Mopar vs Mallory vs Delco type internals. A few posts with tips on how to get some idea of the advance on the bench.
4. Observe the wire positions on the 5 sided plug. Write down the colors relative to position. Position matters.
Top of the pentagon is the power connection (light blue in diagram below). Join this to the to the ignition run wire (J2-dark blue or dark blue with stripe).
View attachment 1716342905
Do this as follows:
Route the ECU power wire alongside the factory wire harness and then to the ballast resistor.
Install an insulated 1/4" push-on terminal to the ECU power wire.
Install a piggy back onto the ballast resistor post where the J2 (Blue) wire(s) get attached. (arrow on diagram above).
View attachment 1716342906 <= Piggyback allows installation of two female terminals onto one male terminal.
5. Identify the wire on the ECU plug to the left of the power. That's the connection to coil negative. It connects to ground instead of the points.
Route that along the wire harness so its supported and protected. Install the appriate size ring terminal and attach to the coil negative post.
6. Route the ECU distributor wires to the distributor plug and connect.
View attachment 1716342910