Even though the American car companies offered compact cars starting with the 1960 models, and filled in the gap with midsize cars a few years later, the carmakers held onto the idea that their full-size cars defined and represented them well into the 1970s. And while the large cars were often the standard-bearers for styling and design trends, even before the first oil crisis in 1973 plenty of people did not need or want a full-size car.
For many buyers midsize models often represented a sweet spot in terms of exterior size and interior room: not too much of the former, not too little of the latter. The midsize models of the mid-to-late 1960s were roughly the same size in overall length and weight, and were equipped with engines of roughly the same or greater size and power output, as the standard cars of 10 to 15 years earlier. (It would have been interesting to see how the American car market developed if full-size cars hadn't kept getting bigger well into the 1970s, but that's a tangent I'll leave for another time.)
As the 1960s rolled into the 1970s, the bloat of full-size models began to afflict midsize cars as well. By 1974, when the federal government required all new cars to have bumpers capable of withstanding a 5-mph impact, the length of a midsize car ranged from about 206" (for a Chevrolet Malibu two-door) to 215" (for a Ford Torino four-door), during a period when two-door and four-door body styles were typically built on different wheelbase lengths; people bought four-door cars because their back seats were roomier. (For comparison purposes, current midsize cars like a 2015 Honda Accord or Ford Fusion typically land at about 190-192 inches in overall length.)
But before that happened, midsize cars were still fairly sensibly sized and attractive. The convertibles and sporty two-door models like the Pontiac GTO and Dodge Coronet R/T tend to get the most attention from collectors, but today I'm going to express my appreciation and enthusiasm for a plain-Jane four-door sedan. Why? Watching TV shows like Adam-12 while growing up may have something to do with it, where it seemed like all the patrol cars were Plymouth Satellites or Dodge Coronets (later, when the LAPD inexplicably switched to AMC Matadors, the show did as well).
the one I featured earlier this year), but what I'd choose for my fantasy garage is a 1970 Dodge Coronet 500 four-door sedan. For unexplainable reasons I love its scowling face, and I have since I first saw one in the parking lot of my elementary school in the early 1970s. The 500 was the highest trim level available for a Coronet in 1970, and I figure it would be more interesting to have one of those than a plain base model that would look like an old detective's car.
It's not too surprising that the internet isn't exactly bursting with images of these cars, but it is a little disappointing. Curbside Classic did a writeup on a '69 Coronet 440 sedan a couple of years back with a few good pictures of the car in question, but there isn't much else that would be useful here, so you'll just have to take my word for it.