Does this sound like the ignition switch?

TF360 said
74 Duster- It's been difficult to start lately. I noticed what I think is a little binding when turning off the key. But here is what is happening- I turn the key and she turns over, no problem, but wont start. I noticed when I go to turn the key off, it starts to fire up. It sounds like " Blup" and then shuts down. I did test power to the coil a while back and it was good. Sound like a key switch?

It could be the switch as that's a location where power to the coil is switched to bypass the ballast resistor. What you describe sounds like there is no power when the switch is in the starting position but when you let go and it goes to "run" it tries to start. I would check to make sure that there is battery voltage at the coil when the switch is in the "start" position.