There is a fusible link coming off of the starter relay/solenoid. When it goes out most of the electrical system will lose power-no radio, door buzzer, ignition or lights.
IIRC the wire is yellow on most Fords, but if not, it will have a little rectangular rubber tag on it identifying it as a fusible link. Sometimes you have to unwrap a few inches of the harness to see it. You can simply pinch along the wire and you will find a soft rubbery spot where the wire inside has burnt out. You can get a replacement fusible link at napa for 5-6 bucks. Resist the urge to use a regular piece of wire, unless you fuse it for the right amperage, which I do not know of the top of my head (but 25 amps comes to mind for some reason)
Sudden electrical failures will almost always be found to be fusible links-but the question remains, what surge caused it to fail? A common culprit is a starter solenoid going bad. Also check all of your grounds and look for any shorts in the wiring running to the starter, If you have headers, they have been known to burn the wire to the starter and create a massive dead short that can literally burn the post off of a battery.
