Re the first post, there are tape recordings of the two speeches and Irving has never denied making them (plus there's many interviews & videos of him making similar comments elsewhere so it wasn't exactly out of character).
Fabricating or manipulating tape recordings should be child's play for a hypothetical organization that can make the world believe in a holocaust that never occurred.
As to his evolving views, you should read this essay ("From Revisionism to Holocaust Denial - David Irving as a Case Study"), particularly the section headed "Crossing the Line".
Did David Irving write that essay? If he didn't write it, then how do I know that it isn't about David Irving's evolving policy of disclosure of attitudes that haven't changed?
I don't think this is a wholly appropriate topic for the lounge
I put it in the lounge to encourage at least casual replies and to allow the thread to quickly sink away if nobody is interested. Can you propose an appropriate place for it on DU?