My 96 Taurus has a switch that activated when the car was jacked up or tapped hard in the rear end. Wouldn't start until the switch was reset. If the 2000
stang has this (? ignorant here -not sure if it does or not), check it.
Other advice is good - battery, terminals, fuseable link, fuses (remember the big one), and try the other key (you do have a second key, right?). Getting cute with the wiring harness bypass could be hazardous with these new cars - lots of delicate little computer brains you can fry - I'd leave this sort of experiment to the very experienced...