340 mismatched heads?

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I'll post this again......

View attachment 1715677417

Thanks @Alaskan_TA .

I have a 73 340 with a Z and O head. I was trying to find out how to decode the date on them. What this attachment you posted is telling us is that there are Z and O heads that are 1.88's and only the 1970 Z and O heads are 2.02"?
Did they make Z and O in 1973 or are these not original to the engine? The engine and trans are original to the car.

My heads have 3418915. Both the Z and O. The Z has a casting date of 10099 and the O is 10249. How is this transferred into a day, month, and year? Just trying to determine if they are 2.02" or 1.88".

Thanks.