unfortunately the little ferules are a tad bigger than the hole for the adjuster ( a different carb top was used).
Possible ways forward
Grind the ferrule down a bit - I did this, watch your fingers on the grinding wheel?
Drill out the carb top
Buy a new carb top, they are available for either adjuster or ferrule - but £15 ish each.
I'm also thinking of a Tuffnel spacer, modified to take some of the downdraft off the carb, this is on a S/W arm alloy head so might well be a bit different on a plunger though
all the best it - Bill