Grand Theft Auto: Motor City.
Set in the 50-60's. You start as a minor thug in the streets of Windy City (Chicago). As you work your way up in the family, you get sent to Motor City (Detroit) to increase your families influence in the auto unions.
Around you grows a sweeping story of political corruption, racial tension, and lots and lots of violence.
Has the heat gotten to hot for you in Motor City?
Flee the country and bunker down in Canada for a while and work on an international crime syndicate.
Not only does this give you the benefit of the distinctive look of the 60's autos, you could add a couple of things that actually tie it in with the automakers (corrupt the union, take prototypes, etc).