Im fairly confident its a poly-block that will accept Hemi heads.
It has a 3-5/8"(std.) bore,so the tops & bottoms of the bores must have 'smileys'
ground into them so the valves wont hit the deck. My dad did this with no problems in the 60s,blown & on Fuel.
However,I want to be sure what I have here.
The casting number alongside the valley surface is 1613129-2.
I searched high & low & couldn't find anything.
Thanks a bunch
tc