how can you identify gt40 cast iron heads?

[glock22_40]

My friend has a gt that was supposed to have gt40 cast iron heads on it, but we have our doubts. How can I tell if the heads are gt40's, or factory units? Also, how can you tell production year of the heads/. Thanks.

 

[Mustang Yawie]

In the front of the head there should be 3 bars, and on one side it should say gt close to one of the front headbolts

 

[maverick0716]

If they're GT-40P heads there'll be four bars on the front of the heads.