74 dart can’t get a spark

If the headlights work that means there is power to the welded splice. It is LIKELY between there and the key switch. --Or at the key switch/ connector itself. Might be the splice itself is bad but that is RARE. DOUBLE check at the ignition switch connector. You can unplug the connector and take the harness end. There is ONE wire that should be hot at all times, which is the feed from the ammeter circuit/ welded splice. Another thing you can check is anything that should be hot at all times, such as brake lights or hazard flashers, or dome lamps. All of that is feed off the "hot" buss in the fuse panel and it also comes from the welded splice