What’s the “H” for on 915 heads?

Well thank you boys! I appreciate the energy and information. I thought both of these heads were “J” head with the post “H” after the part number. Today I open both boxes to inspect before the machine shop drop off and see one is “H” and one is “C” both boxes were marked pass or drivers. Maybe these were drilled for accessories to be specific. I need to check that tomorrow before I drop them off if I remember. But I always thought MoPar heads were swap-able left to right with no troubles. Maybe I’m wrong here.
Both say 360 but the “H” head has a nice straight forward cast in “360.” Whereas the “C” head has this small almost script like “360” cast in. Both are pre emissions exhaust ports. (No extra meat for the possibility of drilled air ports.)