Some of the many inquiries I receive from Old Cars Weekly readers request production numbers and numbers of surviving cars. I can usually help with production numbers, but when it comes to the total number of cars from a specific manufacturer that survive, it's impossible to determine except in two cases: Tuckers and Duesenbergs. These two makes of cars are so low-production and have such a following, many people track each cars' history and whereabouts, and have been doing so for so long, it would be truly amazing if a completely unknown car emerged from a barn or an estate in South America.

The most recent production question came from reader Joe Boccio, who owns two 1968 Pontiac Grand Prix models, one of which is euqipped with a 375-hp 428-cid witha  four-speed. He says, "I do know it is one of 655 produced this way out of 31,711, but I would like to know how many are left on the road. Do you know of a way to obtain a current vehicle registration count (by state or the whole country) of a specific year, make and model?"

Determining exactly how many of nearly any car is almost impossible. A good example of the bad types of estimating is in a recent Sound Your Horn, in which a reader wrote in to say he had a Stutz of the same year/make/model featured in OCW. (In the story, we stated the Stutz was believed to be the last of that kind left. Turns out, that’s not the case. Because of such instances, we’re always careful how we word estimates of remaining cars.)

The only good estimates of remaining cars come from clubs that have registries for specific cars that were low production, and they are never 100 percent, because not everyone is a member, or has heard of the registry. Also, some people simply do not want to give out their information to such registries.

The best estimate people use for determining a survival rate is 10 percent. Given the effects of rust and accident damage, the frequency of salvaging high-mileage cars, etc., this is probably the closest we’ll ever be able to get. So, in this case, there are probably around 65 1968 Pontiac Grand Prix models with the 428-cid/375-hp/4-speed combination left.

However, Pontiac owners should be happy to know that few people can find such specific production numbers as Boccio and other Pontiac owners can for their cars, and that you have access to Pontiac Historical Services for documenting your car — it’s a luxury few owners have for documenting their cars.