I’m guessing Brodix B1-mc small block heads. Look like a lot of work would be needed. Wish I had better pictures and more info. If they are indeed MC heads here’s some numbers from Stan’s website.
Cool. I don't remember ever seeing the extra row of head bolts on those for the R3 blocks. Very interesting. I would love to see someone do a modern port job and valve job and see how they perform.
Nobody ever talks about the short side radius size and shape, and I have always been curious.