Actually, three...
First off, will a 383 motor cause any interference problems with a power steering gearbox in an A body? I know the oil pump sticks out on the left front of the engine at the bottom and I wonder if that might cause space utilization problems, but, maybe not. I dunno...
Second, I want to tell you that the "rebuilders" who work with companies like Auto Zone, Pep Boys, Carquest, Checkers/Schucks/Kragen, Advance Auto, and O'Reillys sometimes are not the most technically conscientious mechanics in the world.
I bought a "rebuilt" power steering box from Pep Boys for my A body (1972 Valiant with power steering), and by the time it had 4,000 miles on it, it had serious issues, such as almost half-a-turn of free play on center.
They offered to replace it, but I got my money back and ordered one from Firm Feel
http://tinyurl.com/62ew6v and it has proven to be worth every penny I spent, with virtually no "play" on center, no leaks, and a nice increase in road feel. I think they call it "cop car" valving...
Good luck with your steering box!