I think the low-trim, service line of '61 Plymouths were called the Savoy, and I'm pretty sure Car 54 was a '61 Plymouth Savoy. The car under it looks like it could be either a Savoy or a Belvedere; if it's an unmarked police unit it's probably a Savoy.

The station wagon appears to be a 1961 Plymouth Sport Suburban.

Thank you *very much* for posting these, as "Car 54" most certainly deserves a spot here at IMCDB. Unfortunately there's never been an official DVD release so finding images is difficult. I think I have a '63 episode here at home and I'll try to save the images from that one sometime.