Cylinder Head Casting Date?

Is there a way to determine the date, or approximate date, that a cylinder head was cast? I have a pair of 915 J heads. I read in the Mopar Performance "A ENGINES" book that pre 72 heads need hardened exhaust seats added, but the 72 & later heads already have them. My heads have 360 cast into them. They each have a place that looks like a plate was screwed into the mold. One has the number 05050 on it & the other has 05080. They also have a place with an arrow that points to a 1,2, or 3, and a clock face type of thing with an arrow. I tried looking in the tech archive but the info I found there was too general. It would be nice if I didn't have to pay for hardened seats.


:burnout: