RARE/VIRGIN Early 360 Block 341xxxx

There is a spot on block that I need to mag
and make sure it is a casting flaw and not a crack
My son said he did look at it and is a surface blem only
but I will double check it.
It is just a normal casting mark.

I may have one more left 341xxxx
It is 020 with less than 1,000 miles