In the early eighties, with his battered mobile home and camper business facing yet another interest-rate-induced slump, Paul Zimmer sought new fortunes in a market where buyers paid in cash: a burgeoning cottage industry of neoclassic cars.

Boutique makers such as Clénet Coachworks and Excalibur had already carved out a niche over previous decades building custom cars on modern underpinnings with extravagant bodywork inspired by the best of the Classic Era.

In 1981, nascent Zimmer Motor Cars Corp. would launch its own neoclassic, sketched up by Paul Zimmer himself.

Built in the company’s Pompano Beach, Florida facility previously used to create custom interiors for conversion-vans, Zimmer would apply that expertise along with the legacy company’s experience working with fiberglass to create the Golden Spirit.

Starting with a new Ford Mustang, the body would be cut apart with only the roof and doors remaining.

The wheelbase was extended from 104 to 142 inches and custom fiberglass...