When Red and Eric were talking in the driveway there was a van right next to them. The tail lights shown on that particular model van were only produced in the mid 80's and later.
Chevy van rear lights up to 1985 were recessed:
Chevy van rear lights 1986 and later were 'bubbled' (as shown in this episode):
These picturess are not the best way to show this, but it can be seen that the lights are clearly different, and it is obviously the latter style that is used in the show. How can a mid 80's van be in a show about life in the late 70's?