The 258(original) in my '83 CJ5 has an "83" cast on the head on the drivers side front of the head.I have another 258 that originally came out of a 1983 Scrambler.It also has the "83" cast in the same spot.The 258 in my sons 1989 YJ has an "82" in this spot.I am assuming this is a 1982 engine.Anybody know if I'm correct in this assumption?

This guy has some casting number info:

link to monsterslayer (http://www.monsterslayer.com/jeep/258CastingIDs.htm)

Look at the actual casting number, not the build date, and you will be certain of what you have.