I know that the Mark VIII is rated anywhere from 4000-4500, typically referenced as 4300CFM from anything I have read. The Taurus I tend to see at 3800CFM, again with a range of numbers from 3800 and up. I have no way of knowing what the stock fans pull, but I know that it is nowhere near 4000CFM.
Also, I dropped a Taurus fan in there yesterday evening, and it fits like a glove. It is not as wide as stock, but that should not be an issue, as the Mark VIII fan is about the same width.