I have built alot of circle track engines with 906 vortec heads 11:01 solid flat tappet cam 600 HP carb and its no problem to make over 500 horse.
People race flow benches all the time you have such a thing a quanity of flow and then you have quality of flow!!!!
I have seen where the Bowtie heads will out flow the Vortec heads but the Vortec heads make more power!!!
The Vortec heads have raised intake ports and exhaust ports and a fast burn chamber its not a bad head.
The Mexican casting are not as good as they have to small of intake runner 158 CC compared to the non mexican castins which are a true 170 CC intake runner.