More often corroded and poor connectors and crimps cause excessive resistance. Whenever resistance is added into the equation it causes a voltage drop, and heat. Most common area of A Body electrical corrosion problems is at bulkhead connector. Most common spot for meltdown from too high current is bulkhead connector, second would probably be connection to amp gage caused by loose connections, and third corroded glass tube fuse holder.
The second problem was caused by Chrysler bean counters in front office forcing engineers to design wire harness to minimum wire gage, resulting in voltage drop in any high draw circuit such as headlight circuit.
If one wants to add high draw equipment to an A Body plan on doing some wire harness upgrading such as heaver gage conductors and installing relays to operate them. There are multiple posting covering different methods of upgrading wiring here, and over at /6 dot org.
