Those are the newer/better Edelbrock castings of the old MP heads. They will flow a little better than the MP heads when ported. I have the older MP heads on my motor that were CNC ported at MCH.
Depending on the rest of the combo, 900+ hp isn't a problem at all out of those heads.

edit...those aren't the same head I don't think. Top looks like the older MP casting like I have. Bottom is the newer version of the same heads cast by Edelbrock for MP. They are slightly different, but I don't think there'd be any real issue using the pair together.