90' Mustang GT. Car will not start. Turn key on @ nothing works. No noise of fuel pump turning on, no power to starter solonide, Changed TFM on distributor. Nothing seems to make the car come alive. Wasn't able to locate a ignition ground switch.
So you're saying everything is dead, just the same as if there was no battery in the car? If that's correct, start by checking the two large copper nuts on the starter relay / solenoid on the inner fender. Ford likes to use one of them as a common tie point for all of the other electrical circuits.
If those nuts are tight, use a test light or digital voltmeter to follow the battery cables to see where voltage is lost. That will be the point to look for a bad connection.