Mine originally flowed 378 at .700 and I think 380 at.800.
I had 2.30 intake valves put in and saw a five to six percent jump in flow, (399 cfm at .800) but ZERO gains.
there was a dip in flow around .400 that may account for part of the lack of gain. The heads flow about the same as before at that point.
I wouldn't worry so much about the ultimate numbers as I would how fast guys are going with them. That is a much better bench mark. My best ET/mph was before the 2.3 valve mods, with a 280/288/110 cam with .765 intake lift. I put a 283/296/112 cam in with .775 lift and got very little if any improvement.
-1 heads are about all done somewhere around 850 to 900 hp, depending on build.