Seat belt light just hooks to the time delay relay that is used to light the ignition switch & dash light switch...

Low fuel warning has a low fuel relay mounted to the right of the glove box, the fuel sender lead goes to the fuel gauge like normal but the lead to the gauge from the IVR is disconnected & in it's place a feed from the low fuel relay plugs onto that gauge terminal...

The door ajar switches are located at the mid rear jamb area & they simply provide a ground path for the door ajar light which is powered at all times...