Old game shows like To Tell the Truth have a classic charm, perhaps because they're antiquated by today's standard. Three guys stand in a police line-up and claim, "My name is Johnston McCulley." Were a program like this broadcast today, people would search for McCulley's Facebook page or related articles, then claim they "knew it was him all along."
McCulley's segment doesn't begin until the 17:00 mark, after the mandatory Geritol commercial. Kick back and enjoy the episode in its entirety. It's only 25:24 of your life.
This is the closest I've found to a television or radio interview with Johnston McCulley. It's a good excuse to remind everyone Zorro: The Complete Pulp Adventures is available from Bold Venture Press.