Factual error: Even though this film is set in 1965, Burlington Northern locomotives can be seen. The railroad was formed in 1970. Also, an EMD GP40-2 can be seen at the beginning of the film, but the first ones were built in 1972.
Factual error: When Ponyboy and Johnny leave the bar after going there to see Dally, there is a song playing on the juke box called 'Jack Daniels if you please' by David Allan Coe. This song was written and released in 1978 but the movie takes place in the '60s.
Factual error: The story is set in 1965, yet it shows many modern (as of filming in 1983) pieces of medical equipment, such as disposable plastic nasal cannula, modern plastic IV tubing and cut offs, etc. Also most hospitals in the 1960s still had open wards with many patients cordoned off by curtains, instead of private rooms as depicted in the movie.
Chosen answer: Simple question, simple answer. Throughout the movie, and on the way to the rumble, he wears a (different colored) plaid shirt, white tee, blue jeans (on the day of the rumble he asks Darry "and where are my jeans?), and worn out tennis shoes.