[blykins]

If he wants to keep the same powerband and manners, my gut says that we wouldn't hit 450.

That's 1.28 hp/ci, but doing it without a single plane intake, considerably larger cam, 10-10.5:1, etc., may prove to be a challenge.

I don't like to peak a hydraulic roller motor any higher than 5500. That will let you shift at 6000 and will hopefully keep you out of valve float.