[Texas Tom]

In answer to questions:

-All electrical components (horn, lights) work just fine.
-System is wired per diagrams for 12V systems found in various Model A publications.
-Battery shows 12.6 volts on analog voltmeter prior to starting engine.
-When engine is started, voltage on voltmeter drops to 10.5V or so.
-NAPA store says both my alternators (1-wire) are fine.
-CarQuest store says my 12V battery (which is sealed and is 15 months old) is fine.

Tomorrow I'll try an alternate battery and will report results.

Thanks to all for your assistance.