More electrically issuses

There are a number of fuses that IF blown could cause the alternator not to work. Do you have a Volt-Ohm Meter (VOM) and are you willing to use it?

Test for key on power in and out of fuse F1.20 and F2.5. Use a known good ground. Best to also use a test light that "loads" the circuit.

Confirm +12 volts at the alternator B+ terminal. Use a known good ground. This will test the fusible links.

Confirm key on +12 volts at the alternator YE/WH wire. Again, use a known good ground.

1999-2004 MY fuse panel schedule:
https://www.allfordmustangs.com/for...r-swap-wont-fire-please-help.html#post2669271

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/