an electrical nightmare , please help , 1972 dart

I put in a used swap meet alternator . It seems to be charging normally right now . At first , it was still overcharging . After twisting the wire connections , below the steering column , during a test , it went to charging normally . I will chase that later . For now , i want to fix chase possible bad ground .

The headlights and front turn signals don't light up . With the headlight switch on , the side marker lights , the fender mounted turn signals , the directional and high beam indicators in the dash , all light up solid . With everything connected , the foot dimmer switch is getting power to all three terminals . About 7 or 8 volts each . The headlight terminals are only getting 0.18 v .

I have cleaned up the grounds on the radiator support , the block to battery cable , and the block to firewall strap . Is there a way to test the grounds or the wires ? Are there any more grounds for the headlights ? Does the starter cable connections have anything to do with that ? One of those looks somewhat corroded at the connection .
After checking the grounds (I use a OHM meter at the ground connections, to be sure you are getting a 100% continuity) Example: ground wire to body or "-" on battery. Next I would remove the firewall electrical plug at the block (a known problem with these older cars) and clean terminals and again use dielectric grease. Check the AMP wire (should be the largest wire) for any burning and replace if needed. Make sure the connections (nuts) are tight at the AMP gauge.