I don't think those EQ heads will support over 525HP from what I've seen... just won't flow enough. Nothing wroung with them...
My ported W2's flow 280 and the HP was 575 with the original set-up it had... ported M-1 intake, 580 lift cam, 13.5 to 1, 3.79 stroke, 4.030 bore... yada yada yada.