Only by buying the complet package from the Pontiac Historical people. (can't find the URL right now)
The VIN only codes the most basic info on the car (coupe or GT) and that's it.
Are you missing the tag on the indide front wheel well? I can hardly read one of mine but by looking at the complet list of codes and nowing what my car has I've been able to guess at some of the missing codes. The problem is that some of the codes I can read do not match my car. Theroy is that at some point the liner was switched for some reason and the tag is not for my car. I am going to buy the kit next spring and the have a local decal shop make me a new one (they will not make one without the GM documents).