Agree with Jerry. Unless there is changes made to get more air IN then the factory manifold is capable of getting all the exhaust out with some to spare. The siamesed port stovebolt head is just not a performance piece. If you come up with a 12 port head then the story changes but not much with just a four main bearing cap block. GM stalled for 30+ years after Ford and Chrysler had a good head before finally coming out with the Atlas engine. The Stovebolt engine is EXCELLENT for what it was designed---a low rpm engine with very good torque but some insist on entering their plow horse into the Kentucky Derby. If your honest and call it eye candy then that's acceptable.

Evan