Later model 318's have air injection ports right underneath the exhaust ports that will need plugged. Drill, tap use set screws.

Mock up the exhaust manifolds with the engine on the stand, later heads wit the injection ports have added material that may interfere with the fit, you can grind down the extra to clear.

Timing cover holes in the block, early blocks have an extra hole later covers do no have, it will pee coolant. Double check that, it is almost covered, but it will pee anyway.