Apparently Holtkamp was so impressed by the Mercedes transporter that he wanted one like it; of course the only way to do that was to build his own.. He started with a Mercedes 300 chassis and fitted Porsche suspension parts, a Chevy El Camino cab and a Corvette V8.. The handling was said to be somewhat wayward (lethal actually..) so he had to rebuilt the whole thing longer and with the engine further back, losing the Mercedes-like bodywork in the process.
Another pic:
