Those numbers are a little on the heavy side from what I've been told, typical on them as delivered intakes is in the 370 +/- range. The Posted numbers are probably "optimum numbers" and everything varies due to weather conditions, Pipe, no Pipe, bore size, Guy doing the bowl blend getting tired, Ect.
Charlie and Scott have been working on them and they are getting higher numbers but I'm not sure your going to see those kinds of numbers out of them, especially the 325cfm on the factory style exhaust.
I would call one of them up and discuss it with them and figure out what you need. if your looking for heads with that kind of flow maybe a set of A460's would be a better choice.
I just purchased a set from Scott and with the out of the box heads on a 521" motor with a XR292R It looks like 700-725 hp is possible.