What’s the “H” for on 915 heads?

I’m my not to sure about that date thing. While a “J” head certainly was made in a certain bracket of years, the reason for the letters in the first place we to make an easy way to identify them from the 318 heads. The factory workers don’t have time or are taught the difference in heads. A head is a head is a head and this here engine needs a head, RIGHT NOW because I have a long line of engines that need heads right now for the next car in line…
Don’t think just do and don’t worry about it say the company.

So 318’s were getting 340 heads and 340’s were getting 318 heads until the introduction of the letter heads.

The different letters were just an identification maker as to the nest series of head that was being made. The difference is hard to see. So ask a head porter where to look, IF they know a Chrysler heads.