Hi olbob,
Welcome to PPRuNe.
That's very interesting information, but it spoils my fantasy. I had thought that perhaps there was a Model 717 tucked away in a hangar somewhere, that was a dreadful failure, never to be spoken of on pain of death!
That certainly doesn't apply to the KC-135.
Then of course, Boeing marketers couldn't stomach the thought of selling an aircraft called the MD-80 and attached the 717 label to it. Has anyone actually used the 717 name in the real world?