A lesson in humility and back to basics. Even though I had 12.6 volts at the starter and at the ignition switch, I pulled the intake out of the way and wiggled the positive battery cable and the headlights came on. There must have been enough contact to allow voltage to come through the corrosion. Once I wiggled the battery cable and got the headlights, I turned the ignition over to start it with nothing but a click and the headlights went off again. I tried the cable wiggle a couple of times followed by a starting attempt with the same results, a click and loss of lights. Not until I removed the cable connector and vigorously cleaned the post and inside of the connector would it start without arcing out. A lesson learned for the simple stuff. Thanks for the help from everyone and hopefully this will help someone down the road.