Well, is from that's a good answer. GT350 from Mr Rouch cause he had to walk 350 feet from the building where they built manufactored stangs to the building where he had his modified. Nothing to do with HP or anything else. Now what does the 500 stand for?? I don't know. Now just watching a car show on cable. They put out 96,000 units of Chargers in 1964. I was a young in but remember driving one,, from there on till today. Right before the stang stung.