questions about my heads

[Slik69]

I have 462264 no cast into my heads and according to the chart they are 75-86 year head. But my heads are stamped 70 on this insude..and have a single trianle between cyl #2./4 It's really been a challenge trying to figure out what heads these are.

http://www.frontiernet.net/~ennis/castingno.html

Could the years listed just be incorrect. I don't see how something that's stamped into a head could be wrong.