Some 45 years after Jack Ruby was convicted in 1964 of slaying Lee Harvey Oswald, his celebrated "irresistible impulse" defense is being challenged—by Ruby's own words. That's right, the most investigated political assassination in history, the JFK-Oswald story, has yet another shocker. Never-before-revealed interview notes taken by a Ruby biographer and heading to auction strongly suggest that Ruby did not act on impulse when he came face to face with Oswald at the Dallas Police Station. The notes the biographer used to write stories sold to newspapers to build a legal defense fund quote Ruby saying he "intended" to gun down Oswald. In the story draft, Ruby describes seeing Oswald: "I lost my senses . . . I pulled out my gun and took a couple of steps . . . they could have blown my head off. I only shot him once . . . I guess I intended —I don't know what." But defense lawyer Melvin Belli edited out that and other potentially incriminating Ruby quotes. Alexander Auctions Presi-dent Bill Panagopulos, whose sale takes place November 6 and 7, tells us, "Undoubtedly, much more could be read into these notes." He predicts they'll sell for up to $3,000.