The Sunbird started out as a car that wanted to be sporty. It was intended to compete in the same class as the Ford Mustang II, along with several small foreign sports cars from Japan. It was sold as a 2 door coupe, 3 door hatchback, and 2 door station wagon. The base engine was the 2300 I4, but the top option was a 305 Chevy V8 in 1978 and 1979, so there was a lot of room under the hood for a compact car.
The H body Sunbird, along with the V8 engine and the station wagon body style, were dropped after 1980. There would be no Sunbird for the 1981 model year.
The J2000 Sunbird for 1982 was a J Body car with front wheel drive. The V6 and V8 engines would not be seen again, with the only engine options being 4 cylinders.
Starting in the mid 1980's, the Pontiac Sunbird received an optional GT trim. The Sunbird GT got a turbocharged I4 engine, and later on a V6 engine. Performance was considerably better than the standard Sunbird.
The Sunbird would be replaced by the Sunfire after 1994. You can still find plenty of the later model Sunbirds on the used car market. They are just about identical to the Chevrolet Cavalier, which is more common. You can also find them listed on eBay, generally for $2000 or less. Parts are also sold on eBay.