[Jack21]

Fords use a separate starter solenoid to power the starter, and sometimes the contacts will weld together. When that happens, the starter will keep turning. Time for a new solenoid, $12 - $18. Ford solenoids also supply 12 volts during start to the coil, bypassing the ballast resistor. The ballast resistor reduces coil voltage during run to about 7 volts. Ballast resistors are frequent ignition culprits. Chryslers were the worst.

$29.95 at Radio Shack will get you a good enough volt-ohm meter for automotive and household use.

Consider upgrading to an aftermarket ignition system such as an MSD, Crane, or Accel. Also consider an aftermarket starter like the Powermaster.