When leaving the police station, the office reminds the Arnolds to "buckle up". However, no US states had seat belt laws in place until 1984, with New York being the first.
During one of the driving shots a 1986 Buick Skylark and a Grumman LLV USPS truck can be seen in the background. The Skylark is a 5th generation model Built from model years 1985-1991 while the Grumman LLV was built for the USPS service starting in 1987. This episode takes place in 1972.
Kevin asks Jack for the keys to the car, but on his 16th birthday he was given his own set of keys. He should only have to ask if he can drive the car, not for the keys themselves.