My answer, the movie is The Sucker (Le Corniaud) 1965 film.

Le Corniaud is a comedy movie, where Marechal innocent guy going to Paris has car accident with Saroyan who is a mob boss. Saroyan then offers Marechal to drive his friend's Cadillac from Naples to Bordeaux. The cadillac will be filled with stolen gold, diamond, heroin and stuff.

1. The gemstones refer to the precious stones hidden in the car.
2. Le Sucre or sugar refers to the sugar cubes that Mickey keeps throwing into the Saroyan's car fuel tank.
3. Red Austin Healey 3000 is the car driven by Italian mobsters.
4. Cadillac is the main car where all heroin, gold and precious stones are hidden.

Still decoding the others. :-)