Big Block Exhaust Manifolds

What's the deal with the idea that there is a "power steering" manifold.

My manifold has the right part number, but they came off my manual steering 383-s fastback. They have the identation that another member showed as making it a "power steering" manifold.

My guess is that there is no difference. Anybody out there that knows for sure?

Rod

PS - manifolds are not for sale.