* Block casting: The engine blocks themselves are different castings. While the external dimensions might be similar, internal passages, bolt patterns, and other details will vary.
* Cylinder heads: Buick and Chevy heads are not interchangeable. They have different combustion chamber designs, valve angles, and bolt patterns.
* Intake Manifold: The intake manifold will be unique to the Buick 350.
* Other components: Other parts like the crankshaft, connecting rods, and oil pump are also different.
While some parts *might* be similar or even interchangeable (aftermarket parts, for example), the core engine is distinct and not directly swappable without significant modification.
