The French license plate on the 1971 Lincoln Mk III used to smuggle the heroin is 18 LU 13. The real life French Connection car, a 1960 Buick Invicta, had French plate 18 LU 75. According to Robin Moore, the Invicta was popular with drug smugglers in the early 1960s because it had a large space under the body behind each front wheel well. Most of the heroin was hidden in these spaces in the French Connection car, but some was hidden under the rocker panels, as depicted in the film.