360 rebuild or throw away ???

That bolt hole should be dry , but I might dig around inside the water jacket with a hunk of wire and make sure that core shift or corrosion hasn't turned it into a boat anchor.
It does get close above the coolant port.
If it just got drilled a little deep when they machined the block , it won't hurt anything.
I do like the idea of sealant just because crankcase pressure will take the path of least resistance and it could piddle oil out of there.