Stock Appearing is just that STOCK APPEARING. Keyword there being "Appearing"
For example, our short runner evo manifold with the california special heat shield is allowed, as it is Stock Appearing.
Ported stock manifolds are allowed as well. As for the FP Race, if it had a stock heat shield on it, sure.
As for the interior question. The rules state full interior. That means FULL INTERIOR, or Full Interior Appearance.
Aftermarket seats are acceptable as well.