That is a casting line.
The 4 long water pump bolt threads need to be sealed with Aviation Sealer as they go into the water jacket.
View attachment 1716114107
Also the lower 2 bolts on the driver's side where power steering bracket mounts to block.
Extream Warning, do not use too long of bolts on the 2 lower driver's front bolts or you can punch them through #1 cylinder wall and destroy your block.
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