First, the exhaust ports on the 350 Oldsmobile exhaust manifold may not align exactly with the exhaust ports on the 403 engine. To address this, you may need to have the exhaust manifold modified or use an exhaust manifold adapter to ensure a proper fit.
Second, the exhaust manifold gaskets may not be the same size or shape for the 350 Oldsmobile and 403 engines. You will likely need to obtain the correct exhaust manifold gaskets to ensure a proper seal between the exhaust manifold and the cylinder head.
It's important to note that attempting to install an exhaust manifold from a different engine model without the necessary modifications may result in performance issues, exhaust leaks, or even damage to the engine. If you are unsure about the compatibility of the 350 Oldsmobile exhaust manifold with your 403 engine, it is best to consult with a qualified mechanic or automotive professional to avoid potential problems.
