Depending on how tight the shot is on the police car and the officers inside, sometimes the rearview mirror on the windshield is in place, sometimes it's been removed to not obstruct the view of the characters as they speak.
When the all-points bulletin is sent out for Hector Munoz, his car is described as a "1964 Chevy Impala". It's actually a 1963 Impala.
When Officer Cooper is driving around with Officer Sherman on his first day, Cooper calls what appears to be a prostitute over to the cruiser. She leans in the open window and chats them up, revealing she's an undercover vice squad cop. She would not blown her cover that way. Moments later, Cooper pulls up next to an unmarked car containing two undercover cops. There's no way they'd blow cover like that.