Check that your ground strap to frame connection is good and clean, as in take it loose, scrape any paint away and smear a little grease on it and the cable end. Do the same thing with the starter connections. If your battery is good, then it has to be something fairly simple given that its either dead or fires right up.
"East were the Dead kings and the remembered sepulchres; West was the grass." Archibald MacLeish