Looking for Cylinder Head Recommendations

I think the hughes number is naturally aspirated. 625hp is about 310cfm which I find just a bit happy for any SB ede head. Most all the numbers I've ever seen for those heads on a calibrated SF600 bench @ 28 are in the high 280 low 290 range. Those hughes kit come with the stock ede valve springs IIRC, so that's another part of the equation which is probably not useful to you.

Keep in mind that by putting boost to the engine changes everything regarding port flow. With a turbo and pair of heads that flow in the 270's, I bet you could get 600+.

Being on the west coast, look up Brian Hafliger at Indio Motor Machine 760-347-5493. He's very good at porting SB Ede heads and reasonable.