The Pontiac Custom S was slated to be called the Pontiac TC, but that name just didn't click with Pontiac executives.
For a one-year car, there were an amazing number of different body styles on the Custom S. They included the 2 door convertible, hardtop coupe, 4 door sedan, sports coupe, 4 door hardtop, and even a station wagon. If it has a vent window in the front door it's a sports coupe.
Despite its muscle car looks, the Custom S was sold standard with a I6 engine that made just 175 horsepower. There was a better 6 cylinder available with the Sprint package that made 230 horsepower. For those who really wanted performance, there was the V8 engine with a 4 barrel carb that made 330 horsepower.
The Custom S was not particularly rare in the year it was produced, but because it was only produced for one year they can all be consider rare today. The easiest way to find one to buy is on eBay, where you can also find some parts to fix them up.