I knew that this image looked familiar. It appears in McPherson's Superior book on page 70 along with the story of the concepts. The picture must have been scanned from that book. According to the picture caption and text, there were apparently more than one of these made up but,(paraphrasing) Superior required substatial changes made to the Cadillac commercial chassis to accommodate the extra loads. Cadillac wouldn't, or couldn't, make the changes and so the project was dropped. The original idea was to introduce vehicles of this type with the 1976 models. These could have been a neat solution to the problems facing the industry at the time.