I'm not a w2 guru by any means, but I believe there are at least 3 "generations" of them.

The first basically look like stock heads externally.

The second have a more smoothed over exterior, no ribs around the outer bolt holes, and iirc they have "Mopar W2" cast into them on the exhaust side of the head.
The letters are indented in, not raised.

The third has the ribs by the bolt holes, letters raised.

There might be other versions or variations within those versions as well.