I checked all the fuses this evening, and didn't find anything obviously blown. Under the dash and under the hood. Might have to do more searching for some wiring diagrams. The gauges, AC & fan, turn signals, power windows, automatic lights, and 115v power outlet do not work. The lights/fogs work manually, brake lights, mirrors, interior lights, power locks, wipers/washers, cruise, console, 12v plug, hatch release and radio DO all work. Several of the indicator lights work also - door open, cruise, airbag, and the AC control lights work too.
I worked on my son's radio, pulled it out and re-installed the new one several times adding the remote mic and parking brake override and never disconnected the battery. Lucky I guess!
The crank in the Mustang broke right at the front of the motor over 3 years ago. Rod through the pan and balancer wobbles about 1"out of position. I guess it lost oil pressure and popped on me while accelerating on the freeway feeder road. I have a replacement short block, newer heads, and everything needed to rebuild the new motor, just need to find the time to do it! When it is cooler!
Broke timing chain, cover and crank:
I had the bright idea to swap out the non working 03 Nav radio with the stock one from my son's 06 so I could at least see the stations and change the presets while I tear into the Nav radio to see if I can figure out why the screen does not work all the time. Per people on here it looks to be a direct fit, and the wiring harness has the same plugs. Well, now the radio works, but the gauges, automatic lights, turn signal, power outlet, AC system, and probably a few other things dont work!!! All I did was remove the dash plate, unbolt & unplug the radio; the wiring harness was attached to the radio so I tugged on it a bit to remove it, and replace the radio. Must have a short or something in the dash wiring, or maybe there are some crossed wires in the plugs for the 03 vs 06 radios. The seller did tell me not to use the power port on the dash since it did short out once when someone pushed the lighter in and it blew a fuse, knocking out a bunch of stuff on the car. I guess I'm pulling the dash apart this wekend if I can't find a blown fuse. It is too dang hot around here to even attempt working on it during the evenings. Should have just left it alone, like my wife said!!! 
I can agree with you on the heat though, im in south florida & its WAYYYY too hot during the summertime to do ANY work on my car. I do all my maintenance ( minus oil changes ) during the winter and spring now. I learned my lesson doing my brakes one year 
Im sure you will figure out out what the problem is. Hey whats the deal with your 5.0 ? do you still drive it ? I dont I ever seen pics of it. I used to have a 1990 5.0 hatch. Wow i miss that car 
How quickly we forget new things and revert back to our old habits of driving a manual car. After all, I drove one daily for about 26 years!