Manual steering box with 35 spline
It should be a 5/8"-36 spline all the boxes from 62-up used this spline.
There are several different spline sizes with in the 5/8"-36 size. 600", 605", and .620" on the major diameter, but a Mopar takes one with the .620" major
outside diameter. This is the same size a Stiletto rack uses.
I have never seen one that was a 1/2", so if it really is you got something odd there.
Tom