Steering coupler's are different!

I'm putting this out there hoping for some help from the community. In the process of replacing and rebuilding my 67 dart manual steering column and coupler. I ordered what I thought was an exact replacement for my car. Well when I started to put the new coupler in there is a distinct difference between my old one and my new one. The new coupler has a small hole at the top where the lid and gasket clips on. I'm assuming I need to purchase or find a dowel or roll pin to put in there to fill hole? Is this pin to hold in the parts inside the coupler? Can I just fill the hole or if I have to buy a new pin what is it and where can I get it? See the attached photo to reference. Any help much appreciated.

Carl