440 source aluminum water pump housing, Big block..

Demonic said

So one is 1/2 NPT pipe thread and the other one is 3/4"? Or the one hole isn't tapped correctly? Pics?

Click to expand...

The one im having trouble with is 1/2, the other one is smaller and i have a plug for it. Am i correct in thinking these holes use NPT threads? I will get some pics.