Whats the deal with 340s?

When I was a kid, one of my brothers had a 340 Demon. Some guy built it. I don't know what all that consisted of, but headers, cam, aluminum intake and a 850 dp Holley was what I knew. This car raced any and every thing that was willing.... and it never lost. Built 454 Chevelles, you name it. It never went to the strip, but wow, what a street warrior.