[scooder]

Just reminded me Mart,
In the past I swapped a drag link end from over to under the steering arm, what I did was break apart an old steering joint (Rod end), ground some flats on the ball part for purchase, cut a couple of slots in the taper, and shaped the taper from the slots so it made a rudimentary reaming tool. And used this to cut the steering arm taper from the other direction. Wasn't the greatest tool in the box, but it's what I had. As you said, the taper only has to go half way through the arm to do the job.
Martin.