Hopefully it won't be mythical, as Dawson's been wanting to fight Tarver for a minute. If/when it happens, Tarver's days as a major player come to a screeching halt (if not already). Dawson by wide UD. The best available version of Tarver, vs. Dawson - same result, but a little closer on the cards. Tarver probably even fucks around and scores a knockdown, but fails to finish.
I think Tarver at his best beats Dawson and via KO. Six or seven rounds. Today? Tarver would have to make 175. If he did? Dawson wins a close decision.