OK, Jonah sent me some pictures:
First, Jonah’s engine is a 1965 model, not a 1957. Next, it appears as though someone has changed the original fixed high speed jet to the adjustable needle kit. I’m "assssuming" the initial setting is the same for this kit vs the original style adjustable needle. Now, I have never seen one of these kits but am again assuming there must be some sort of threaded insert that goes in front of this needle so it has something to seat into…
Again, have never seen/worked with one of these kits….