The car that I really remember was a yellow van that my Dad must had bought empty and he added the seats, etc. There were two front seats and two back seat that faced the sliding door, so yes, we always were riding sideways. Under one of the side seats was an 8 track tape player that most likely was playing the Beach Boys, Kenny Rogers, or the Beatles.
This car was also custom upholstered by my father with shag green carpeting, he most have gotten a deal on that carpet. In the back half of the van he built a platform plywood bed about 4 ft high and 6ft deep, and yes it was covered in green carpet. Under the platform was a lot of storage for all our camping gear that you could access through the back doors of the van. We had the best time on the platform bed, we could sleep on long trips or pretend it was a stage and sing. But the best was roll around back and forth as the van turned back and forth and up and down on the windy roads (this was before any seat belt law). We would roll back and forth, bumping into each other and laughing. Or you could lay back there and just look out the window (which was at eye level when laying down) and watch the world go by.
This was one kooky van and we had it a very long time, I had to take my drivers license test with this beast and yes, I had to take the test twice because of parallel parking!