Niwot resident Brian Foster was looking for a "project car" when he spotted something special in an out-of-the-way garage in eastern Colorado.

"It was just wasting away in somebody's backyard," he said.

Underneath a minor coat of rust was a 1973 Chevrolet Camaro, one of the earliest models of what would become the classic American muscle car of the 1980s.

"I knew when I saw it that they're a...