After doing a little bit of research, I have come to a conclusion that even though the Mystery Machine was supposedly based on a 1968 Chevrolet Sportvan 108, there really was no certain answer of what it really was. A Ford Econo-line was used in the movie and there is much chatter that it was not really based on anything particular because it was a cartoon. It has been debated if it is a Corvair, a Ford, and well… a VW. I say let’s go with a Volkswagen, I am not sure that Fred, Velma, Daphne, Shaggy, and Scooby would mind!
Here are some very GROOVY tributes to the Mystery Machine:
If you like to read a bit more on Scooby Doo: