There is a torrent available on Demonoid and presumably elsewhere, consisting of a 3-hour-plus compilation of JC appearances spanning his first call circa mid-90s to his final call to Art in 2008. I'm sure it does not include every single call he made to Art, and it excludes calls to the other hosts (including Noory), but it's a big heap o' JC to swallow all at once.
Listening to this recently, as I have, I came to the conclusions that (A) yes, JC is a put-on and always was and (B) it is the creation and performance of a single individual. Listening to the bits chronologically, you can hear both the voice and the character develop, but there's never any question that it's the SAME voice. As for the final and clinching proof, to me, that it was a put on--and if it seems odd that I didn't see it as a sham from the beginning, bear in mind that I was raised with a very fundamentalist/evangelical background, so people very much like JC were part of my real existence--during one of his rants, in this case on race issues, he says to Art, "It's time to turn on the showers and fire the ovens, for the queers and the coons and the reds and the Jews." At which point Art said that was enough and ended the call.
But obviously Art is not enough of a Pink Floyd fan to recognize that line as a lyric from their 1979 album, THE WALL, a concept album in which the central character, a rock star named Pink, imagines himself cut off from the rest of humanity by a psycho-emotional wall, with each bad choice or circumstance representing a "brick". Towards the end, he imagines himself as a fascist dictator, ready to rid his audience (and the world) of those seen as unfit. Of course, it was all meant as a parody/comment--the author, Roger Waters, is one of the great humanitarian/liberals of our age, and he and his associates have always been horrified by those who have only seen the surface of those lines and not the context or subtext.
In any case, that, to me, was the final evidence that JC was simply a character, though one created and performed by an obviously talented (and probably undiscovered or hobby-only) voice actor who is clearly intelligent and equally informed by world news, entertainment, pop culture and history. The way JC would twist and blend those things, and filter them through that particular religious lens, is unique to someone who has had direct exposure to that mentality.
Now here's the punchline. I'm driving home a month or two ago, on a Friday night, not long after I'd listened to the JC marathon, and I turn Coast on. Noory is interviewing UFO Phil, who wrote and recorded the closing song that Noory has used on Friday nights for many years ("I turned on my radio in the middle of the night..."). And I noticed something.
The voice, the cadence, the rhythm, the inflection....WERE EXACTLY THE SAME AS JC. The accent, tone and delivery were different, but everything else was the same.
Which means, if I'm right, that JC and UFO Phil are both creations of the same voice actor, and that he/they are on the inside of the Coast machinery, and have been for sometime. How this happened, who can say? I really think for the first several years, maybe even the first decade, this guy just called the show, and when he got in and assailed Art, Art took it at face value. But I think sometime during the early years of Noory, a formal contact was made, a professional (if sub rosa) agreement was breached, and JC/Phil went on the payroll. Not in any huge way, of course--more in a sort of comic relief/occasional plant sense--but still.
Think about it. It makes sense. And it's nice to have my own little Coast conspiracy theory.