Can you prove this Star Wars rumor true? Is there a comic where Darth Vader is not Anankin?

I heard that before George Lucas came with the idea of the Empire Strikes Back story, that there was a comic where Obi Wan fought with his apprentice Darth Vader (before he turns out to be Anankin Skywalker himself in ESB) anyone know if there is a picture of the duel between them?