Engine/Trans Date Codes

Wondering if there is an easy way to tell what year a 3.4 engine was made-----and what year tranny is attached to it. (so I can see if an engine swap will work)

I have on 03 Impala---and the engine in the car has an 03 stamped into the intake casting, right in front of the throttle body. I have another engine, which may be out of an 2000 Impala that has an 00 stamped in that same place in the intake. Is that how I tell what year these engines are---or is there a serial # I should look for?

And on the transmission, (same car) there is a white plastic tag attached on the passenger rear of the trans, with the following code: 611RDBW125J. Does that tag and code allow me to determine when the trans was built?

Any and all advice would be great. Thx