273 / 318 Exhaust Manifold Question

Has anyone ever tried to port/gasket match a pair of OEM 273/318 A body exhaust manifolds? Any noticeable difference in power?

I have a 67 barracuda with a 273 Commando mill, was wondering if I should gasket match the original exhaust manifolds or install the Flowtech full length headers I have. Ground clearance is an issue, my car sits fairly low at the moment.

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