Rick,
That is exactly what I did on the Ranger which is very similar to the viking in regard to the clamp tube. I kept the clamp tube and simply used the KNX mod with it. I also used variable bias on the clamp tube to vary the transmit power. It still clamps and works fine on CW or if there is loss of drive.
See the schematic at my site on the Ranger mod for details.
http://www.crompton.com/hamradio/JohnsonRanger/RangerRestoration.html