That would be about right---the first of the "new generation" or P series Pirellis was the P7, in sizes for exotic cars, circa 1975-76, followed soon after by a less expensive version called the P6, intended for performance cars. The P3 was a basic tire that attempted to associate itself with the other two by having a similar name. They came out some time around 1980. In my opinion, they were miserable---soft and mushy compared to a Michelin XZX or Kleber V12GTS. Not only that, but the rubber they were made of was inferior, and quickly oxidized to a dull gray color on the sidewalls, which showed a network of tiny cracks in less than three years, whereas Michelins remained smooth, shiny and black for 2-3 times as long. as you can probably tell, I've never liked Pirellis much.

My 75 still had one of those, that escaped the recall somehow, as a spare when I first got it circa 1994. It was the only example of that notorious tire I can recall ever having seen.

Sedans and wagons had different size tires when new---185/70 on sedans, and plain 185 (equivalent to 80 series) on the wagons---and probably different brands as well. A few years earlier they were even more different---140s, until at least 72, came with 165-15 radials if they were sedans, and 6.85-15 bias plies if they were wagons.

It may also be that US cars were equipped with Firestones, as the 500 was, prior to the recall, much hyped as a premium product, and cars for the rest of the world came with the more familiar European brands.