Detective Toschi and the 1978 Letter

I agree with most everyone that the 1978 letter is fake but the 1974 letter is real. Why? Because only Zodiac would have understood or put together the logic behind the joke of the Exorcist (which was personal to him). He wrote the Belli letter as a joke in response to the show in which the fake Z called in asking in a very pathetic way for help. In a letter to Belli dashed off after the show aired, Z mimicks this pathetic tone, saying that he'd truly like to stop killing but can't because of this thing inside him; he needs help etc. Then, years later, he sees the Exorcist, in which Regan has a devil inside her and the words HELP ME appear on her BEL-LI.
Now who other than Z would see the humor in that?

I agree rand.