I just bought an engine that was advertised as a 1998 Mustang GT V8. I noticed it says 7/22/97 on the valve cover with the numbers 8A100AA. The current blown engine in my car says 8A101AA. So is this a motor from a 1997?
If so does that mean anything for me when i go for the swap?
Not really. If there are any differences, it will be simple stuff like an oil level sender in the oil pan. Or one may have an oil cooler and the other not.
You would notice it if there were issues like Windsor vs Romeo blocks. If there are the same number of bolts on the valve covers, they are the same.
OBTW, it's common for the motors to be older than the car's MY. The motor is built well before the car is put together.