How does the steering column mount?

You don't need "big bolts" They are either 5/16 or 3/8" I don't remember. They either have captive large washers or you can use separate washers. The holes are big to allow aligning the column with the shaft at the box.

As mentioned, there is additional clamp up at the column.

Go to MyMopar if you don't have one and download (free) the closest thing you can get to a correct service manual and parts manual. You may have to settle for Dodge vs plymouth