Which power steering pump should I get?

I have a 68 Dart GTS. Originally a 340, now a 360. Not sure what year 360.

The power steering pump, brackets, lines are all missing, and I would like to look for another setup. Problem is, I dont know whether to look for a setup for a 1968, a 340, or a 360. Or does it even matter?

Like I said, I need everything, but I dont want to buy something that wont fit or work correctly.