Head casting numbers

If I were a betting man, I would guess that it's a slant six head, cast during a shift around 5 o'clock on August 16th, 1966. The CDPD stands for Chrysler, Dodge, Plymouth, Desoto. It's just a logo.

It's a 66-74 slant six head, with 1.62" and 1.36" valves.

But like I said, just a guess. Someone else may know more.