Proflow cast iron exhaust manifolds have been designed to hug close to the engine block so they fit into a wide variety of replacement and engine-swap applications. Their contoured design aims the exhaust directly at the exit port for improved flow. Being cast iron means they will provide years of leak-free performance with less under hood noise than traditional headers. Plus, their short design means you can route exhaust tubing close to your frame/floor pan for maximum ground clearance. Not compatible with 2004-2006 GTO starters and bellhousings.