Unless they are the 69 heads because they are closed chamber.
But it realy depends on what year your block is and what heads were on it origanally.
The letter C is for the 60's and D is for the 70's and so on.
So if you see C7 that means it's a 1967, hope this helps some.
Once you ID your block and heads we can give you a idea of what you have good or bad. Kurt