Shelby is supposed to have used the distance from one building to another to come up with the number. He said that if the car was a success, the name wouldn't mater and if it was a failure, nobody would remember. There are more details to the story which I'm sure some of our member will fill in.
Ol Shel asked how far it was from the race shop (or is it engine shop?) to the assembly building. It was 350 feet. What Rsimkins said was correct. Plus, I lost count of how many people asked me it it had a 350 C.I engine. I think it was more snake oil from the old man.....