The Vortec requires a specific Vortec intake manifold available from both GM Performance Parts and Edelbrock. On dozens of dyno-tests, ... Since this is an OEM iron head, ...

Here is how you can build a 447 horsepower Vortec small-block ... sharing many features with the excellent OEM Vortec ... we went with a Professional Products Crosswind two-plane intake manifold.

The Vortec heads require a few different parts to bolt on, such as a special intake manifold from Edelbrock that uses only eight intake bolts (5/16-18 x 1 1/2-inch long) and a unique gasket.