383/438 Build

Are you going to use the one piece metal gasket and valley pan as the factory used, or are you going to a solid valley cover and separate intake paper or composite gaskets? Those don't look like they were enlarged to max wedge size, so I say you just need to trim the gaskets open to fit. I have no experience with the actual stealth heads, but it's common to adjust gasket openings after heads have been opened up.