I've never worked on a Super, but all other 105 series spiders and sprints that I have played with use allen screws to hold the two halves of the steering column shround together. Metric allen screws, naturally.
As I recall, these screws are in at least two different lengths (the pair on the left side is different from the pair on the right side), and they are fairly unique - that is, if you lose one, you won't find its replacement at the corner hardware store.