I have not worked on your model truck, but I would guess you need to remove a nut from the end of the pitman shaft. Then with a puller remove the pitman arm.
Or is the arm clamped on the shaft with a cross bolt, even easier to remove?

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-