Olds 394 engine side plugs?

Hello!

I'm mounting my engine and transmission back in the car after a big restoration. I rebuilt the engine about 1-2 years ago and can't remember what those holes are for? (see pictures)

There are one of those holes on each side.

Are they supposed to be left empty or do I need some sort of plug/bolt? If so, does anyone know what size?

//Andy from Sweden

 

If they are blind holes (tooling) they don't need plugs. If they go into water or oil, they do. I bet they don't.

 

No need for anything in those holes......they are blind