An investigator is trying to identify the private ambulance used in a 1956 kidnapping on the streets of Manhattan. The ambulance transported a drugged victim from a subway station to a private airfield on Long Island. In 1956, private ambulance services in New York City were licensed and regulated. The FBI investigated the case and compiled over 10,000 pages of records. The investigator has access to the FBI file but cannot locate the ambulance. Construct the most effective open-source research strategy to identify the vehicle, using only records and databases that would have existed in 1956 and might still be archived today.