73 power drain

Help! I have a power drain on 73 rag mustang with key out of ingition. I've narrowed it down to the courtesy light circuit by process of fuse elimination and have unhooked all connectors to no avail. Is the seat belt warning buzzer and key-in buzzer tied to this circuit? Currently I have neither working but the seat belt light is operational. Where are they located and how do I check them. Any other ideas appreciated. Thanks.
 
This just happened on my 73--the dome light was stuck on and killed my battery. No amount of opening/closing doors or turning the headlight switch would fix it. What fixed it was to open the drivers door, then depress the door jamb switch completely with my finger. I heard a distinct click from the seat belt stuff under the drivers seat and --- boom the lights went out. Maybe that will work for you too?