Engine Block production date casting numbers

[JKP]

Low Tech question ? how do you read the production date block casting numbers ?

 

[WarWagon]

The later blocks '85 and up have a number sequence cast into the pad on lower drivers side near the 3.8 liter designation
The early blocks mid '75 to '84 have a number sequence on the top of the bell housing flange at the rear of the block.
I'm certain that those numbers will correspond to a date but no dates are actually cast on the blocks.