Classic/Antique Car Repair: 1979 El Camino 350 4brl, starter solenoid, battery cables

Question
Recently I'm having a number of electrical issues with this vehicle.  I replaced the alternator 2 weeks ago.  This morning, hopped in, fired up the engine, let it idle a bit, put it in 'Drive' moved abount 2 feet, and she died.  Turned the key, nothing.  Grabbed to other car and went to work.  This evening I pulled the battery and took it to Auto Zone.  It tested 'good' and they said no dead cells.  On the off chance, I bought new battery cables and installed them.  Nothing.  I've been very pleased (until this morning) at the difference a new alternator made in the way she was running, but now I'm a bit lost.  As i type this I have a battery charger on it, just in case Auto Zone was wrong.  Any ideas where to go from here?

Answer
Turning the key, nothing would by no means point me to the battery.  If you have enough power to make your headlights come on, the engine should turn over. If your park/nuetral switch has gone out, that would give you nothing. If you ignition switch has failed , that would give you nothing. If the starter solenoid has gone out, that would still give you dash lights and indicators, just the starter would not turn.