After George cuts Jackie's hair, her formerly streaked tresses are a uniform blonde tint, although he had not colored her hair.
The Coca-Cola can George drinks from while chatting with Lorna is a post-1968 design.
During the final party scene, the song "Good Shepherd" from Jefferson Airplane's "Volunteers" album is prominently featured. "Volunteers" was not released until November 1969, a year after the events in the film.
While in the bank at beginning of movie, you can clearly see a 1972 Ford Torino through the storefront glass window.