why? are you TRYING to kill your low end/ midrange power?

I'd imagine that the bore/stroke difference between a 600 and 1000 would make the cylinder spacing different enough that it's be a pain, if at all possible, to fit, not to mention the downdraft part of the header is probably longer, which would lessen your ground clearance.

what's the supposed gain in putting a 1000 header on a 600, other than at WFO and damn near redline?