Did all 67 390 cars have a exhaust valve that faced the passenger side of the engine compartment ? My car has the C7 passenger side exhaust manifold and is a correct date for my build and not the C6 manifold which would let the valve face the passenger side of the engine compartment where the C7 part wont let this happen because of its slightly different shape. My engine was built April 26 67.
All of the GT390 cars had the valve in '67. They were used through the entire '67 model year and halfway through the '68 model year as well.
The C7 exhaust manifold is the correct one for Mustang / Cougar. The C6 manifold will fit but it is actually a '66 Fairlane / Comet part.