There are four different places to look for the head part numbers that I’m aware of for the various years.
1. Under the water ports where the intake manifold bolts up.
2. Exhaust port side of the heads.
3. In the valve spring area under the valve covers.
4. On the deck side of the heads.
Another option for cylinder head identification is to measure the combustion chambers and the intake valve size. Are there freeze plugs or core plugs in the ends of the heads? That would be another clue to watch out for.