Understanding Merc Manifolds 3.7

[karayj]

Trying to understand exhaust elbows the top picture is going to show my current exhaust.
Today I picked up a spare elbow and I'm wondering as far as the grooves are concerned and the gaskets, why do they not match up? For instance a gasket will have three slots but the manifold will have four openings. I'm just confused is one of the openings to allow any freeze into the manifold thus into the engine how does this all work because I'm seeing these openings and I'm seeing these gaskets that have two openings or four openings it's very confusing.

My Manifold. What are the holes in the blue for?

The gasket has NO opening for the sides slots..

My gasket is below

I not sure what my current elbow looks like ? Maybe this type


This is a backup I bought for future use if needed.
Unless mine should be like this

 

[nola mike]

Can't remember off the top of my head what mine looked like, but iirc the gaskets and reservoir are different depending on whether the manifold is cast or aluminum.

 

[karayj]

I guess I am trying to understand the slots in the elbow and manifold.
The single one on the elbow seems to be a fill opening. I am trying to understand the ones on the exhaust.