Power steering

Of course you need the P.S. gear box. Look for a later model gear box as they are all the same and the later boxes will be Chrysler firm feel. The P.S. steering column is shorter with the components of the column being different from the manual steering shaft.
You'll also have to procure the power steering pump, brackets and the correct pulleys to operate the pump.
The p.s. column shouldn't be too hard to come by. A lot of Mopar guys are going to manual steering.