Great examples FFC's fanatical attention to detail are the period cars he shows in the films. I've been a car nut since I was a little kid, and the Fifties are my milieu. Here are my two favorites for authenticity in GFII:

--The car drives Michael in Havana is a '57 Mercury Montclair. Not a very rare car when it was filmed, but totally authentic: original green/cream two-tone paint job, bumper slightly askew from hard use (hence not a collector car borrowed for the movie). Nice touch: it has a tinny, European-style horn--just what a Cuban driver of that era would have put in his car.
--The car that brings Michael back to his Tahoe estate after Cuba is a '58 Chrysler Imperial Crown Ghia limo, one of only about a dozen made in that year and, with body by Ghia of Turin (Italy), the most expensive US car ($13k). He could have chosen from one of many, many Cadillac limos of that era. But, trust FFC: He gets one of the rarest cars ever--and shows it for maybe 10 seconds.

My favorites in GF are the '43 Alfa Romeo 6C2500 sports sedan that Apollonia gets blown up in; the '54 Chrysler Imperial limo that brings Michael to Moe Green's hotel, and the '54 Packard Patrician that Michael gets into after the christening. Other faves in II are: Frank Pentangeli's '57 Cadillac Eldorado coupe; Fredo's '57 Mercedes Benz 300SL gullwing coupe (in a deleted scene at the beginning of Anthony's party--worth well over $1M today); '58 Chrysler New Yorker driven by Johnny Ola on the way to Roth's home in Miami (probably Roth's car--exactly what a rich Jew would have owned), and the '57 Ford Custom 300 driven right behind it by Michael (exactly what Avis would have rented to him,in original two-tone red and black). I also liked the enormous '58 Lincoln Connie that hit Willie Cicci in the shootout outside Richie's bar.

Any faves of yours?