Pitman arms

[glider_6969]

Can someone tell me what the difference is between the pitman arm from a manual steering box and the one for a power steering box? I have both boxes on my bench, the one from my 68 and the one I want to use can be found in 80-85 trucks, and comparing or trying to figure out why I can't use the stock pitman arm from the manual box. Both boxes have the nut that holds the arm on to the shafts that seem to be the same size.....

what am I missing... any help would be great thanks.