The 828 area code on the telephone number displayed in the background during the "gas and dash" scene wasn't in use until 1998, when it was introduced in North Carolina. In 1978, all U.S. area codes had a middle digit of zero or one. Chicago's area code was 312 at the time the film was set, and including an area code in a local telephone number would not have been necessary, as ten digit dialing was still years away.
In the montage of driving through the streets, a street sign for "Los Angeles" street is clearly visible as are the buildings on the Los Angeles Street in Los Angeles, California. Des Plaines doesn't have a Los Angeles Street.