My dad came through and found a copy of the ad I was looking for in the last blog entry. Although this one is a call for artists, I'm sure if there was a writer's ad, it would have been very similar. Anyway, this ad originally appeared in the September 23, 1956 edition of "The New York Times".
I had contacted Sam Viviano of "Mad" and he did not have a copy and once my dad located this in a local library to me, I sent Sam a copy for the "Mad" archives. Sam said that this ad also is rumored to have been answered by Mort Drucker and Norman Mingo, among others.
The writer ad was supposed to have been responded to by Paul Laikin and Frank Jacobs, but they may have just responded to this same ad, placed by Al Feldstein when Harvey Kurtzman left "Mad" and took virtually the entire staff with him.