Not 100% correct.
96-97 1/2 have the true GT40 heads F3ZE casting #. All the later years have GT40P's. You can tell by the plug angle, as the GT40P are straighter and the GT40 heads have "GT" cast right in them and 3 bars at the front of the heads vs. 4 for the GT40P.
I went and looked for pics to show...here is a GT40P
GTP cast in the corner..
GT40 head.... see 3 bars and the GT in the front corner