I don't think there is anything wrong with adding a high volume pump to a 5.7L Hemi, I believe the issue is that it might suck the oil pan dry before oil can work its way back to the pan. So the lesson is to make sure you have a large enough sump if you plan on using a high volume pump.
This might be particularly important for those of us doing the swap it is my belief (correct me if I'm wrong) that the Milodon pans actually reduce the oil capacity by about a quart. Thus adding a high volume pump while simultaneously reducing the oil capacity of the motor might not be the best thing to do.
Regards,
Joe Dokes