Answer: Neither of the numbers you gave is the correct casting number.
The water pump is part number C8AE 8501-A. This number is what would appear on the outside of the cardboard box containing the water pump. This number does not appear anywhere on any water pump.
The main casting of the water pump has the number C8AE 8505 - H on the passenger side. Here's a picture of one. The date code is below the bearing housing. In this case the date code is 8B10, representing February 10, 1968.