Where I first became aware of the song is on the radio and Williams himself performing his song on TV, I think during the Smother Brothers summer replacement show that was hosted by Glen Campbell.
I went to track down that recording, and think I found it. But all the better is that the person who uploaded the video attached it to another video of the song.
Now, on the surface, it would almost seem "sacriligious" to have another recording of the song since it is SO iconic to Mason Williams. But when I say this other interpretation is brilliant, you should understand that it's performed by perhaps the favorite guitar artist of my longtime pal Dr. Greg Van Buskirk -- a fellow named Tommy Emmanuel. At Greg's repeated suggestions, I watched several videos of Tommy Emmanuel, and they've all lived up to his high praise. This one of "Classical Gas" is a virtuoso performance. And it's world's different from Mason William's original, yet the foundation is there throughout.
I wouldn't say which is better. The technical achievement of Emmanuel is remarkable. The purity of Mason Williams is poetic. It's not only personal taste which you prefer, but I'd suggest that they are companion pieces that support each other.
The only thing I know for sure is that if Dr. Buzz has not seen this version by his beloved Tommy Emmanuel (which he may well have, including live in concert), he is going to be in heaven.