Not Getting 12 Volts at Coil

Try taking the distributer out, spin it by hand with the ign. switch in the run posistion. With a spark plug taken out and grounded, you should be able to see if the spark is hotter. Do not do this with a bunch of fuel in the cylinders as it might blow apart your muffler.
My car had a similar problem. It turned out to be a rebuilt starter that had a short in it. It was draining the ign. system of voltage when I turned the car over.