no fire

If you get one spark when you release the key to the run position the ignition switch could be the fault and it could be the ballast resistor or its connections. Check those terminals too.
I posted a pic of a 73 model wiring harness failure in another members parts wanted thread. Those kind of failures come and go with heat too. Use a volt meter to verify 12 volts. Much less than 12 will light up a test light and fool you. Hope this helps