The numbers photo you supplied is the engine assembly date info. The 1970 and 1971 engines were cast in 1969 and then assembled shortly thereafter. They were then stored away til orders came in to match them up with a car. April 17 of 1969 is not 13 days earlier. It is a year and 13 days - if your car built in April/May of 1970.
Here is a photo of my old 1971 hemicuda ragtops assembly info - it was built a little more than a year before the car in 1970 for a May, 1971 car.
The 1970 and 1971 cars had 1969 dated blocks, if that is of any help. The foundry that made the blocks had cast so many that they kept using them for two more years in production cars. If you ever find a 1970 or 71 cast block is most likely one of the rare (and valuable) high-nickel content, over the counter, blocks that the racers loved due to their strength. While it is unlikely it is your original block if the serial number is not the same, weirder things have happened (like when I found the block from a hemi '70 Charger built on the assembly line one car before mine and was 17 digits away from my VIN).
Do you have a photo of the casting date and the area where the VIN is/was on either block?