Marine blocks

I have a marine 86' 360 block and a 72' 340 block. I don't know if there is a difference between the automotive 360 and the 340, but my marine 360 is thicker in several key areas; the mounts are thicker, the area around the core plugs are thicker, the pan rail is thicker, the main saddles are thicker, the front of the block is thicker.
I have photos many photos I took earlier in the year to compare them side by side, some you can visually see the difference, some I have used a caliper.
I cannot attach all of them, so if there is any particular area you would like to see, I can post a few at a time.
Again, I don't know if the difference is marine block vs automotive block, or 360 vs 340