There have been a total of seven generations of the Grand Prix. The first generation was sold from 1962 to 1968. These cars were basically the same car as the Pontiac Catalina, but they had less flashy exterior trim, including less chrome. These cars could be custom built to order with regard to engine size, and a few people opted for the high output Super Duty 421 engine. These are rare and very collectible. Although it was stripped down on the exterior, the performance numbers on the Grand Prix spoke for themselves. This was a high performance car that would help usher in the muscle car era.
The 1969 Grand Prix was redesigned to have more luxury features in the interior while maintaining sporty performance. Once again, the Grand Prix was ahead of its time, helping to kick-start the domestic personal luxury era.
The V6 engine became standard with the fourth generation Grand Prix, sold from 1978 to 1987. The V8 was still an option, and there were several of them, including the 350 Oldsmobile diesel. The 3 speed turbo-matic was now the only transmission option.
The fifth generation Grand Prix was sold from 1988 to 1996, and it introduced the LE, SE, and GT trims. The V8 engine options were gone on this compact car, but a twin dual cam V6 was available. A 4 speed automatic transmission was the one and only trans option.
The sixth generation W body Grand Prix was sold from 1997 to 2003. The top engine was now a L67 SC V6 making 240 horsepower.
The seventh generation Grand Prix will be the last to use that name from Pontiac. The top engine is once again a V8, this one a 303 horsepower beast. The GT and GXP are the top trim options. The car's name might be phased out, but it's really just going to be renamed for the next generation. The G8 will follow the Grand Prix lineage into the future.
These cars are not hard to find on the used car market. If you are looking to buy a used Pontiac Grand Prix, try looking on eBay first to see where the prices are for the year and mileage you plan on buying. To make things even easier, you might just want to buy off eBay. Look for sellers with high feedback and experience selling cars. Also look for some cheap parts on there. I've found some great deals.