Harry's car is a 1974 AMC Ambassador. Stella's car is a 1964 1/2 Plymouth Barracuda (which has the largest backlight ever fitted to an American-made car).
During filming of the lunch scene, Which was done at the Rock Creek Tavern West of Portland, Oregon. Tom Berenger was to eat a burger. After several takes with Berenger trying to take bite of the burger he could not keep a straight face because the burger was made by craft services and was terrible. The cook from the Rock Creek Tavern heard of the situation and made a "real" burger that Berenger could sink his teeth into. After that, filming wrapped for the day.