It may have been an FBI car. The FBI used weird combinations of equipment compared to other government fleets. I had several undercovers from them and they had factory side trim, full wheelcovers, and some even had vinyl roofs to complete the disguise. In the mid-'70's the State of Pennsylvania ran small Fury (B-body) 2-door undercover cars that also were equipped with 'better' exterior trim.

Have you tried getting a Build Card from FCA? That would probably be helpful.