That certainly throws a new wrinkle into things. Thanks for sharing that. It looks like I have some additional research to do before I install a right hand exhaust manifold.
Here’s a picture of the manifolds on my ‘75 318 before I replaced them with 340 manifolds. I tossed the 318 manifolds last year so can’t pull a part number off them.
The car has been in my family since new so I have all the service records, including when the engine was replaced when a wrist pin failed even though the engine only had 25k miles on it. Since it was before I had my licence, I can’t definitively say that ribbed manifold is the original one. However, the 2bbl original carb, alternator, power steering pump and all other accessories from the original 1975 engine were re-installed on the new engine. I would find it odd that the shop would re-install the other original accessories on the new block except for the passengers side exhaust manifold?