During the early 1950s, imaginations of many young car fans were fired by the appearance of flashy, futuristic dream cars from General Motors and Ford. Styling details from these were borrowed and applied to bulky American cars that served as platforms for Spohn's work.
I have no information regarding who did the designs. I suspect clients initially waved dream car photos under Spohn noses and asked for this or that feature to be incorporated. Later on, it's possible that other clients used previous Spohn G.I. customs as inspiration.
The fundamental problem with these efforts was the fact that the basic proportions of the dreams cars were different from the production models that were much taller and perhaps a bit more narrow. So what looked good rotating on an automobile show display turned out awkward, inappropriate and ugly on the Spohn customs. I'm pretty sure that the Spohn people knew they were turning out junk, but survival was at stake. Nevertheless, the firm failed in 1957.
The photos of Spohn customized cars below were found on the internet, and before those images were scanned, they had appeared in 1950s car magazines or perhaps inexpensive perfect-bound car books. So apologies for their poor quality.
Tail fins and other details from the rear were often used on Spohn custom bodies.
On the other hand, the front end styling of Ford's X-100 (alias Continental-X) was a popular borrowed theme.
One example shown below made use of the XP-300's grille design.