 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.