[ngoma]

Yes make sure the leak is not actually from the headgasket right there in the middle. Common place for headgasket to leak oil out right there, looks like it is coming from the lower mounting ear of the vacuum pump.

But if you can verify it is actually leaking from the vacuum pump, then likely the new o-ring will seal it up.

NOTE: When removing the vacuum pump do not let the plunger rod slip out. It's two ends are different enough (can be hard to tell by eye) that the wrong side against the cam lobe will quickly wear it out. If it keeps wanting to slide out, take it out and set it aside in a way that you can reinstall it in the same orientation when reattaching the vacuum pump.