Big Block Cylinder Heads "915 vs 906"

From what I have seen, the 915's will increase the compression almost a full point, but have port flow issues compaired to the 906's. With that said, both can have the larger valves installed and have the bowls worked to perform equally. With THAT said, after the performance mods are done, it is just a decision on what compression is needed with your combo. I hope this helps.