74 Duster Fusible Link
If you're not great with electrical, do yourself a favor.
Print out the under hood and dash wiring harness pages, biggest you can make them. Get a highlighter and going between the two, highlight everywhere that gets power through the fusible link. Don't forget the power after the ign switch.
Once you've done that, start thinking of ways to isolate parts of the harness. Fuses that can be pulled, connectors that can be undone, etc
Set your meter to ohm, if it's a model that can beep when there's sub-one ohm, turn that on.
Unhook the bulkhead connector that has the fusible link.
Probe the body side of the bulkhead, in the fusible link port.
Other lead to the body, on a cleanish ground point.
If there's a short (and there is). You should see zero ohms, or like 0.2.
If shows open, double check that you're in the connector right, and then turn on the key.
Does the meter show a short?
Now you know if it's before or after the ign switch.
Once you know that, it's time to use that highlighted harness picture and start unhooking items.
ONE AT A TIME!!
Proceed until you find the short and fix it