I have taken the valve covers off of my heads and i see 302 on them so I am assuming they are 302 heads and then there are another set of numbers on the heads right above the rocker arms. Would that be a casting number??
an example of a casting number would be as follows C8ZE, or possibly C8OE. The date code would be stamped inside the rocker area near the edge and would read something like 8D28. You should also see a 2V or 4V stamping near the date code. Some 302 heads were made for 4bbl engines, and some for 2 bbl, not sure exactly what differed in each head. Your 302 heads would not have a '66 stamping number as the engine was not produced until the '68 model year. Post the numbers and we can find out the month and day your heads were cast.
The actual casting #'s that are used to ID the heads are located underneath the intake ports. But the date code that's inside the valve cover, will help in narrowing down what head they actually are.