The J30 column-shift transmission will not affect installing PS on your rig. The easiest/cheapest PS install on a 40/45/55 Series is the so-called "mini-truck" conversion. Search in the 40/55 Section for "Bill Dorry" brackets and other info on this swap.
the steering box on the tree shifter holds the linkage once its removed you will have to go to floor shift or do some serious fab work to keep the 3 on the tree .i dont know if there is a kit that retains the stock linkage or not good luck
part of it uses the box for the long rod on top of the colum .it might be tough to go to power steering and keep the 3 on the tree.i checked on my 69 and 65 to make sure .i think most people that go to power steering on the old three on the tree have floor shifts .it would make the conversion a lot easier good luck
the part that holds the long shaft is clamped to the steering box you may be able to keep it if you go later 40 power steering. I do not know I went floor shift. my three on the tree was very sloppy.