Dead ignition

So the car will not start. I just replaced the ignition/key switch. I am wondering if the new ignition switch is not wired the same as the old one. I had my daughter turn the car over and only got 1 spark when I tested it with an old plug I had. I also had 5 volts at the coil and when she keyed to car it dropped to zero, which explains it only firing once. Any one have an idea of what I should do next?
Randy-

73, 340 dart….