Hi,
I personally know some of the real characters and I have researched this story for years, including travelling to TX.
this is my favortie movie ever, but most of it is inaccurate. ironically, the accurate parts are the parts about the huge amout of vehicles in the chase, the media coverage, and the publich support the couples recieve. I even visited the real gas station where the couple and their hostage stopped for food, and they indeed had presents shoved in the their hands by by-standers.
BUT - the real event lasted approximately 6-9 hours and not two days, the couple wanted to see their two children one last time before going to prison, the children were actually at her paretn's custody, and they were her childred from previous marriage. the dialogs in the car are mostly fictional in the film, but they are still briliant in my view.
the film was shot during January - April 1973, so Spielberg was 26 when he made it.
(excuse my typos, I'm not a native English speaker)