Curious, is that a 305, because GM used the log style(inline across all the exhaust ports) vs the 350 that used a manifold that the exhaust curved downward around each spark plug and ran much closer to the engine mounts.
When it comes to flexplates... look at the starter mounting holes on the block, if they are diagnal, you will need the larger diameter 168tooth, if the holes are straight across, you will need the smaller diameter 154tooth, but im willing to bet its straight across, the diagnal holes where used on pre '86 engines i believe.