The dates are 02100 and 03110 so Feb 10 70 and Mar 11 70, one month apart.
Only 68, 69 X heads have 340 on them, all other 70 & up J,U,O,Z, heads have 360 on them.
The reason I say I disagree is because you're wrong. There are j&u heads made after 1970 that do not have 360 cast into them. I'm sorry if this upset you that you are incorrect and I called your attention to it.